07 Jun, 2020
1 commit
-
commit 5bfea2d9b17f1034a68147a8b03b9789af5700f9 upstream.
The original code in mm/mremap.c checks huge pmd by:
if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) {
However, a DAX mapped nvdimm is mapped as huge page (by default) but it
is not transparent huge page (_PAGE_PSE | PAGE_DEVMAP). This commit
changes the condition to include the case.This addresses CVE-2020-10757.
Fixes: 5c7fb56e5e3f ("mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd")
Cc:
Reported-by: Fan Yang
Signed-off-by: Fan Yang
Tested-by: Fan Yang
Tested-by: Dan Williams
Reviewed-by: Dan Williams
Acked-by: Kirill A. Shutemov
Signed-off-by: Linus Torvalds
Signed-off-by: Greg Kroah-Hartman
10 May, 2020
1 commit
-
commit b2a84de2a2deb76a6a51609845341f508c518c03 upstream.
Commit dcde237319e6 ("mm: Avoid creating virtual address aliases in
brk()/mmap()/mremap()") changed mremap() so that only the 'old' address
is untagged, leaving the 'new' address in the form it was passed from
userspace. This prevents the unexpected creation of aliasing virtual
mappings in userspace, but looks a bit odd when you read the code.Add a comment justifying the untagging behaviour in mremap().
Reported-by: Linus Torvalds
Acked-by: Linus Torvalds
Reviewed-by: Catalin Marinas
Signed-off-by: Will Deacon
Signed-off-by: Catalin Marinas
Signed-off-by: Greg Kroah-Hartman
29 Feb, 2020
1 commit
-
commit dcde237319e626d1ec3c9d8b7613032f0fd4663a upstream.
Currently the arm64 kernel ignores the top address byte passed to brk(),
mmap() and mremap(). When the user is not aware of the 56-bit address
limit or relies on the kernel to return an error, untagging such
pointers has the potential to create address aliases in user-space.
Passing a tagged address to munmap(), madvise() is permitted since the
tagged pointer is expected to be inside an existing mapping.The current behaviour breaks the existing glibc malloc() implementation
which relies on brk() with an address beyond 56-bit to be rejected by
the kernel.Remove untagging in the above functions by partially reverting commit
ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk"). In
addition, update the arm64 tagged-address-abi.rst document accordingly.Link: https://bugzilla.redhat.com/1797052
Fixes: ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk")
Cc: # 5.4.x-
Cc: Florian Weimer
Reviewed-by: Andrew Morton
Reported-by: Victor Stinner
Acked-by: Will Deacon
Acked-by: Andrey Konovalov
Signed-off-by: Catalin Marinas
Signed-off-by: Will Deacon
Signed-off-by: Greg Kroah-Hartman
26 Sep, 2019
2 commits
-
There isn't a good reason to differentiate between the user address space
layout modification syscalls and the other memory permission/attributes
ones (e.g. mprotect, madvise) w.r.t. the tagged address ABI. Untag the
user addresses on entry to these functions.Link: http://lkml.kernel.org/r/20190821164730.47450-2-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas
Acked-by: Will Deacon
Acked-by: Andrey Konovalov
Cc: Vincenzo Frascino
Cc: Szabolcs Nagy
Cc: Kevin Brodsky
Cc: Dave P Martin
Cc: Dave Hansen
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.This patch allows tagged pointers to be passed to the following memory
syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect,
mremap, msync, munlock, move_pages.The mmap and mremap syscalls do not currently accept tagged addresses.
Architectures may interpret the tag as a background colour for the
corresponding vma.Link: http://lkml.kernel.org/r/aaf0c0969d46b2feb9017f3e1b3ef3970b633d91.1563904656.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov
Reviewed-by: Khalid Aziz
Reviewed-by: Vincenzo Frascino
Reviewed-by: Catalin Marinas
Reviewed-by: Kees Cook
Cc: Al Viro
Cc: Dave Hansen
Cc: Eric Auger
Cc: Felix Kuehling
Cc: Jens Wiklander
Cc: Mauro Carvalho Chehab
Cc: Mike Rapoport
Cc: Will Deacon
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
15 May, 2019
1 commit
-
CPU page table update can happens for many reasons, not only as a result
of a syscall (munmap(), mprotect(), mremap(), madvise(), ...) but also as
a result of kernel activities (memory compression, reclaim, migration,
...).Users of mmu notifier API track changes to the CPU page table and take
specific action for them. While current API only provide range of virtual
address affected by the change, not why the changes is happening.This patchset do the initial mechanical convertion of all the places that
calls mmu_notifier_range_init to also provide the default MMU_NOTIFY_UNMAP
event as well as the vma if it is know (most invalidation happens against
a given vma). Passing down the vma allows the users of mmu notifier to
inspect the new vma page protection.The MMU_NOTIFY_UNMAP is always the safe default as users of mmu notifier
should assume that every for the range is going away when that event
happens. A latter patch do convert mm call path to use a more appropriate
events for each call.This is done as 2 patches so that no call site is forgotten especialy
as it uses this following coccinelle patch:%vm_mm, E3, E4)
...>@@
expression E1, E2, E3, E4;
identifier FN, VMA;
@@
FN(..., struct vm_area_struct *VMA, ...) {
}@@
expression E1, E2, E3, E4;
identifier FN, VMA;
@@
FN(...) {
struct vm_area_struct *VMA;
}@@
expression E1, E2, E3, E4;
identifier FN;
@@
FN(...) {
}
---------------------------------------------------------------------->%Applied with:
spatch --all-includes --sp-file mmu-notifier.spatch fs/proc/task_mmu.c --in-place
spatch --sp-file mmu-notifier.spatch --dir kernel/events/ --in-place
spatch --sp-file mmu-notifier.spatch --dir mm --in-placeLink: http://lkml.kernel.org/r/20190326164747.24405-6-jglisse@redhat.com
Signed-off-by: Jérôme Glisse
Reviewed-by: Ralph Campbell
Reviewed-by: Ira Weiny
Cc: Christian König
Cc: Joonas Lahtinen
Cc: Jani Nikula
Cc: Rodrigo Vivi
Cc: Jan Kara
Cc: Andrea Arcangeli
Cc: Peter Xu
Cc: Felix Kuehling
Cc: Jason Gunthorpe
Cc: Ross Zwisler
Cc: Dan Williams
Cc: Paolo Bonzini
Cc: Radim Krcmar
Cc: Michal Hocko
Cc: Christian Koenig
Cc: John Hubbard
Cc: Arnd Bergmann
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
06 Mar, 2019
1 commit
-
When using mremap() syscall in addition to MREMAP_FIXED flag, mremap()
calls mremap_to() which does the following:1) unmaps the destination region where we are going to move the map
2) If the new region is going to be smaller, we unmap the last part
of the old regionThen, we will eventually call move_vma() to do the actual move.
move_vma() checks whether we are at least 4 maps below max_map_count
before going further, otherwise it bails out with -ENOMEM. The problem
is that we might have already unmapped the vma's in steps 1) and 2), so
it is not possible for userspace to figure out the state of the vmas
after it gets -ENOMEM, and it gets tricky for userspace to clean up
properly on error path.While it is true that we can return -ENOMEM for more reasons (e.g: see
may_expand_vm() or move_page_tables()), I think that we can avoid this
scenario if we check early in mremap_to() if the operation has high
chances to succeed map-wise.Should that not be the case, we can bail out before we even try to unmap
anything, so we make sure the vma's are left untouched in case we are
likely to be short of maps.The thumb-rule now is to rely on the worst-scenario case we can have.
That is when both vma's (old region and new region) are going to be
split in 3, so we get two more maps to the ones we already hold (one per
each). If current map count + 2 maps still leads us to 4 maps below the
threshold, we are going to pass the check in move_vma().Of course, this is not free, as it might generate false positives when
it is true that we are tight map-wise, but the unmap operation can
release several vma's leading us to a good state.Another approach was also investigated [1], but it may be too much
hassle for what it brings.[1] https://lore.kernel.org/lkml/20190219155320.tkfkwvqk53tfdojt@d104.suse.de/
Link: http://lkml.kernel.org/r/20190226091314.18446-1-osalvador@suse.de
Signed-off-by: Oscar Salvador
Acked-by: Vlastimil Babka
Acked-by: Kirill A. Shutemov
Cc: Hugh Dickins
Cc: Joel Fernandes (Google)
Cc: Yang Shi
Cc: Mel Gorman
Cc: Joel Fernandes
Cc: Cyril Hrubis
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
05 Jan, 2019
2 commits
-
Android needs to mremap large regions of memory during memory management
related operations. The mremap system call can be really slow if THP is
not enabled. The bottleneck is move_page_tables, which is copying each
pte at a time, and can be really slow across a large map. Turning on
THP may not be a viable option, and is not for us. This patch speeds up
the performance for non-THP system by copying at the PMD level when
possible.The speedup is an order of magnitude on x86 (~20x). On a 1GB mremap,
the mremap completion times drops from 3.4-3.6 milliseconds to 144-160
microseconds.Before:
Total mremap time for 1GB data: 3521942 nanoseconds.
Total mremap time for 1GB data: 3449229 nanoseconds.
Total mremap time for 1GB data: 3488230 nanoseconds.After:
Total mremap time for 1GB data: 150279 nanoseconds.
Total mremap time for 1GB data: 144665 nanoseconds.
Total mremap time for 1GB data: 158708 nanoseconds.If THP is enabled the optimization is mostly skipped except in certain
situations.[joel@joelfernandes.org: fix 'move_normal_pmd' unused function warning]
Link: http://lkml.kernel.org/r/20181108224457.GB209347@google.com
Link: http://lkml.kernel.org/r/20181108181201.88826-3-joelaf@google.com
Signed-off-by: Joel Fernandes (Google)
Acked-by: Kirill A. Shutemov
Reviewed-by: William Kucharski
Cc: Julia Lawall
Cc: Michal Hocko
Cc: Will Deacon
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Patch series "Add support for fast mremap".
This series speeds up the mremap(2) syscall by copying page tables at
the PMD level even for non-THP systems. There is concern that the extra
'address' argument that mremap passes to pte_alloc may do something
subtle architecture related in the future that may make the scheme not
work. Also we find that there is no point in passing the 'address' to
pte_alloc since its unused. This patch therefore removes this argument
tree-wide resulting in a nice negative diff as well. Also ensuring
along the way that the enabled architectures do not do anything funky
with the 'address' argument that goes unnoticed by the optimization.Build and boot tested on x86-64. Build tested on arm64. The config
enablement patch for arm64 will be posted in the future after more
testing.The changes were obtained by applying the following Coccinelle script.
(thanks Julia for answering all Coccinelle questions!).
Following fix ups were done manually:
* Removal of address argument from pte_fragment_alloc
* Removal of pte_alloc_one_fast definitions from m68k and microblaze.// Options: --include-headers --no-includes
// Note: I split the 'identifier fn' line, so if you are manually
// running it, please unsplit it so it runs for you.virtual patch
@pte_alloc_func_def depends on patch exists@
identifier E2;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
type T2;
@@fn(...
- , T2 E2
)
{ ... }@pte_alloc_func_proto_noarg depends on patch exists@
type T1, T2, T3, T4;
identifier fn =~ "^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@(
- T3 fn(T1, T2);
+ T3 fn(T1);
|
- T3 fn(T1, T2, T4);
+ T3 fn(T1, T2);
)@pte_alloc_func_proto depends on patch exists@
identifier E1, E2, E4;
type T1, T2, T3, T4;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@(
- T3 fn(T1 E1, T2 E2);
+ T3 fn(T1 E1);
|
- T3 fn(T1 E1, T2 E2, T4 E4);
+ T3 fn(T1 E1, T2 E2);
)@pte_alloc_func_call depends on patch exists@
expression E2;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@fn(...
-, E2
)@pte_alloc_macro depends on patch exists@
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
identifier a, b, c;
expression e;
position p;
@@(
- #define fn(a, b, c) e
+ #define fn(a, b) e
|
- #define fn(a, b) e
+ #define fn(a) e
)Link: http://lkml.kernel.org/r/20181108181201.88826-2-joelaf@google.com
Signed-off-by: Joel Fernandes (Google)
Suggested-by: Kirill A. Shutemov
Acked-by: Kirill A. Shutemov
Cc: Michal Hocko
Cc: Julia Lawall
Cc: Kirill A. Shutemov
Cc: William Kucharski
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
29 Dec, 2018
1 commit
-
To avoid having to change many call sites everytime we want to add a
parameter use a structure to group all parameters for the mmu_notifier
invalidate_range_start/end cakks. No functional changes with this patch.[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/20181205053628.3210-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse
Acked-by: Christian König
Acked-by: Jan Kara
Cc: Matthew Wilcox
Cc: Ross Zwisler
Cc: Dan Williams
Cc: Paolo Bonzini
Cc: Radim Krcmar
Cc: Michal Hocko
Cc: Felix Kuehling
Cc: Ralph Campbell
Cc: John Hubbard
From: Jérôme Glisse
Subject: mm/mmu_notifier: use structure for invalidate_range_start/end calls v3fix build warning in migrate.c when CONFIG_MMU_NOTIFIER=n
Link: http://lkml.kernel.org/r/20181213171330.8489-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
27 Oct, 2018
1 commit
-
Other than munmap, mremap might be used to shrink memory mapping too.
So, it may hold write mmap_sem for long time when shrinking large
mapping, as what commit ("mm: mmap: zap pages with read mmap_sem in
munmap") described.The mremap() will not manipulate vmas anymore after __do_munmap() call for
the mapping shrink use case, so it is safe to downgrade to read mmap_sem.So, the same optimization, which downgrades mmap_sem to read for zapping
pages, is also feasible and reasonable to this case.The period of holding exclusive mmap_sem for shrinking large mapping
would be reduced significantly with this optimization.MREMAP_FIXED and MREMAP_MAYMOVE are more complicated to adopt this
optimization since they need manipulate vmas after do_munmap(),
downgrading mmap_sem may create race window.Simple mapping shrink is the low hanging fruit, and it may cover the
most cases of unmap with munmap together.[akpm@linux-foundation.org: tweak comment]
[yang.shi@linux.alibaba.com: fix unsigned compare against 0 issue]
Link: http://lkml.kernel.org/r/1538687672-17795-2-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1538067582-60038-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi
Acked-by: Vlastimil Babka
Acked-by: Kirill A. Shutemov
Cc: Michal Hocko
Cc: Matthew Wilcox
Cc: Laurent Dufour
Cc: Colin Ian King
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
18 Oct, 2018
1 commit
-
Jann Horn points out that our TLB flushing was subtly wrong for the
mremap() case. What makes mremap() special is that we don't follow the
usual "add page to list of pages to be freed, then flush tlb, and then
free pages". No, mremap() obviously just _moves_ the page from one page
table location to another.That matters, because mremap() thus doesn't directly control the
lifetime of the moved page with a freelist: instead, the lifetime of the
page is controlled by the page table locking, that serializes access to
the entry.As a result, we need to flush the TLB not just before releasing the lock
for the source location (to avoid any concurrent accesses to the entry),
but also before we release the destination page table lock (to avoid the
TLB being flushed after somebody else has already done something to that
page).This also makes the whole "need_flush" logic unnecessary, since we now
always end up flushing the TLB for every valid entry.Reported-and-tested-by: Jann Horn
Acked-by: Will Deacon
Tested-by: Ingo Molnar
Acked-by: Peter Zijlstra (Intel)
Signed-off-by: Linus Torvalds
Signed-off-by: Greg Kroah-Hartman
15 Jun, 2018
1 commit
-
Commit 5d1904204c99 ("mremap: fix race between mremap() and page
cleanning") fixed races between mremap and other operations for both
file-backed and anonymous mappings. The file-backed was the most
critical as it allowed the possibility that data could be changed on a
physical page after page_mkclean returned which could trigger data loss
or data integrity issues.A customer reported that the cost of the TLBs for anonymous regressions
was excessive and resulting in a 30-50% drop in performance overall
since this commit on a microbenchmark. Unfortunately I neither have
access to the test-case nor can I describe what it does other than
saying that mremap operations dominate heavily.This patch removes the LATENCY_LIMIT to handle TLB flushes on a PMD
boundary instead of every 64 pages to reduce the number of TLB
shootdowns by a factor of 8 in the ideal case. LATENCY_LIMIT was almost
certainly used originally to limit the PTL hold times but the latency
savings are likely offset by the cost of IPIs in many cases. This patch
is not reported to completely restore performance but gets it within an
acceptable percentage. The given metric here is simply described as
"higher is better".Baseline that was known good
002: Metric: 91.05
004: Metric: 109.45
008: Metric: 73.08
016: Metric: 58.14
032: Metric: 61.09
064: Metric: 57.76
128: Metric: 55.43Current
001: Metric: 54.98
002: Metric: 56.56
004: Metric: 41.22
008: Metric: 35.96
016: Metric: 36.45
032: Metric: 35.71
064: Metric: 35.73
128: Metric: 34.96With patch
001: Metric: 61.43
002: Metric: 81.64
004: Metric: 67.92
008: Metric: 51.67
016: Metric: 50.47
032: Metric: 52.29
064: Metric: 50.01
128: Metric: 49.04So for low threads, it's not restored but for larger number of threads,
it's closer to the "known good" baseline.Using a different mremap-intensive workload that is not representative
of the real workload there is little difference observed outside of
noise in the headline metrics However, the TLB shootdowns are reduced by
11% on average and at the peak, TLB shootdowns were reduced by 21%.
Interrupts were sampled every second while the workload ran to get those
figures. It's known that the figures will vary as the
non-representative load is non-deterministic.An alternative patch was posted that should have significantly reduced
the TLB flushes but unfortunately it does not perform as well as this
version on the customer test case. If revisited, the two patches can
stack on top of each other.Link: http://lkml.kernel.org/r/20180606183803.k7qaw2xnbvzshv34@techsingularity.net
Signed-off-by: Mel Gorman
Reviewed-by: Andrew Morton
Cc: Nadav Amit
Cc: Dave Hansen
Cc: Michal Hocko
Cc: Vlastimil Babka
Cc: Aaron Lu
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
02 Nov, 2017
1 commit
-
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.By default all files without license information are under the default
license of the kernel, which is GPL version 2.Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if
Reviewed-by: Philippe Ombredanne
Reviewed-by: Thomas Gleixner
Signed-off-by: Greg Kroah-Hartman
09 Sep, 2017
1 commit
-
When THP migration is being used, memory management code needs to handle
pmd migration entries properly. This patch uses !pmd_present() or
is_swap_pmd() (depending on whether pmd_none() needs separate code or
not) to check pmd migration entries at the places where a pmd entry is
present.Since pmd-related code uses split_huge_page(), split_huge_pmd(),
pmd_trans_huge(), pmd_trans_unstable(), or
pmd_none_or_trans_huge_or_clear_bad(), this patch:1. adds pmd migration entry split code in split_huge_pmd(),
2. takes care of pmd migration entries whenever pmd_trans_huge() is present,
3. makes pmd_none_or_trans_huge_or_clear_bad() pmd migration entry aware.
Since split_huge_page() uses split_huge_pmd() and pmd_trans_unstable()
is equivalent to pmd_none_or_trans_huge_or_clear_bad(), we do not change
them.Until this commit, a pmd entry should be:
1. pointing to a pte page,
2. is_swap_pmd(),
3. pmd_trans_huge(),
4. pmd_devmap(), or
5. pmd_none().Signed-off-by: Zi Yan
Cc: Kirill A. Shutemov
Cc: "H. Peter Anvin"
Cc: Anshuman Khandual
Cc: Dave Hansen
Cc: David Nellans
Cc: Ingo Molnar
Cc: Mel Gorman
Cc: Minchan Kim
Cc: Naoya Horiguchi
Cc: Thomas Gleixner
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Sep, 2017
1 commit
-
mremap will attempt to create a 'duplicate' mapping if old_size == 0 is
specified. In the case of private mappings, mremap will actually create
a fresh separate private mapping unrelated to the original. This does
not fit with the design semantics of mremap as the intention is to
create a new mapping based on the original.Therefore, return EINVAL in the case where an attempt is made to
duplicate a private mapping. Also, print a warning message (once) if
such an attempt is made.Link: http://lkml.kernel.org/r/cb9d9f6a-7095-582f-15a5-62643d65c736@oracle.com
Signed-off-by: Mike Kravetz
Acked-by: Michal Hocko
Cc: Andrea Arcangeli
Cc: Aaron Lu
Cc: "Kirill A . Shutemov"
Cc: Vlastimil Babka
Cc: Anshuman Khandual
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
03 Aug, 2017
2 commits
-
When mremap is called with MREMAP_FIXED it unmaps memory at the
destination address without notifying userfaultfd monitor.If the destination were registered with userfaultfd, the monitor has no
way to distinguish between the old and new ranges and to properly relate
the page faults that would occur in the destination region.Fixes: 897ab3e0c49e ("userfaultfd: non-cooperative: add event for memory unmaps")
Link: http://lkml.kernel.org/r/1500276876-3350-1-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport
Acked-by: Pavel Emelyanov
Cc: Andrea Arcangeli
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Nadav Amit identified a theoritical race between page reclaim and
mprotect due to TLB flushes being batched outside of the PTL being held.He described the race as follows:
CPU0 CPU1
---- ----
user accesses memory using RW PTE
[PTE now cached in TLB]
try_to_unmap_one()
==> ptep_get_and_clear()
==> set_tlb_ubc_flush_pending()
mprotect(addr, PROT_READ)
==> change_pte_range()
==> [ PTE non-present - no flush ]user writes using cached RW PTE
...try_to_unmap_flush()
The same type of race exists for reads when protecting for PROT_NONE and
also exists for operations that can leave an old TLB entry behind such
as munmap, mremap and madvise.For some operations like mprotect, it's not necessarily a data integrity
issue but it is a correctness issue as there is a window where an
mprotect that limits access still allows access. For munmap, it's
potentially a data integrity issue although the race is massive as an
munmap, mmap and return to userspace must all complete between the
window when reclaim drops the PTL and flushes the TLB. However, it's
theoritically possible so handle this issue by flushing the mm if
reclaim is potentially currently batching TLB flushes.Other instances where a flush is required for a present pte should be ok
as either the page lock is held preventing parallel reclaim or a page
reference count is elevated preventing a parallel free leading to
corruption. In the case of page_mkclean there isn't an obvious path
that userspace could take advantage of without using the operations that
are guarded by this patch. Other users such as gup as a race with
reclaim looks just at PTEs. huge page variants should be ok as they
don't race with reclaim. mincore only looks at PTEs. userfault also
should be ok as if a parallel reclaim takes place, it will either fault
the page back in or read some of the data before the flush occurs
triggering a fault.Note that a variant of this patch was acked by Andy Lutomirski but this
was for the x86 parts on top of his PCID work which didn't make the 4.13
merge window as expected. His ack is dropped from this version and
there will be a follow-on patch on top of PCID that will include his
ack.[akpm@linux-foundation.org: tweak comments]
[akpm@linux-foundation.org: fix spello]
Link: http://lkml.kernel.org/r/20170717155523.emckq2esjro6hf3z@suse.de
Reported-by: Nadav Amit
Signed-off-by: Mel Gorman
Cc: Andy Lutomirski
Cc: [v4.4+]
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
10 Mar, 2017
1 commit
-
Convert all non-architecture-specific code to 5-level paging.
It's mostly mechanical adding handling one more page table level in
places where we deal with pud_t.Signed-off-by: Kirill A. Shutemov
Acked-by: Michal Hocko
Signed-off-by: Linus Torvalds
25 Feb, 2017
1 commit
-
When a non-cooperative userfaultfd monitor copies pages in the
background, it may encounter regions that were already unmapped.
Addition of UFFD_EVENT_UNMAP allows the uffd monitor to track precisely
changes in the virtual memory layout.Since there might be different uffd contexts for the affected VMAs, we
first should create a temporary representation for the unmap event for
each uffd context and then notify them one by one to the appropriate
userfault file descriptors.The event notification occurs after the mmap_sem has been released.
[arnd@arndb.de: fix nommu build]
Link: http://lkml.kernel.org/r/20170203165141.3665284-1-arnd@arndb.de
[mhocko@suse.com: fix nommu build]
Link: http://lkml.kernel.org/r/20170202091503.GA22823@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/1485542673-24387-3-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport
Signed-off-by: Michal Hocko
Signed-off-by: Arnd Bergmann
Acked-by: Hillf Danton
Cc: Andrea Arcangeli
Cc: "Dr. David Alan Gilbert"
Cc: Mike Kravetz
Cc: Pavel Emelyanov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
23 Feb, 2017
2 commits
-
Optimize the mremap_userfaultfd_complete() interface to pass only the
vm_userfaultfd_ctx pointer through the stack as a microoptimization.Link: http://lkml.kernel.org/r/20161216144821.5183-13-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli
Reported-by: Hillf Danton
Acked-by: Mike Rapoport
Cc: "Dr. David Alan Gilbert"
Cc: Michael Rapoport
Cc: Mike Kravetz
Cc: Pavel Emelyanov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The event denotes that an area [start:end] moves to different location.
Length change isn't reported as "new" addresses, if they appear on the
uffd reader side they will not contain any data and the latter can just
zeromap them.Waiting for the event ACK is also done outside of mmap sem, as for fork
event.Link: http://lkml.kernel.org/r/20161216144821.5183-12-aarcange@redhat.com
Signed-off-by: Pavel Emelyanov
Signed-off-by: Mike Rapoport
Signed-off-by: Andrea Arcangeli
Cc: "Dr. David Alan Gilbert"
Cc: Hillf Danton
Cc: Michael Rapoport
Cc: Mike Kravetz
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
30 Nov, 2016
1 commit
-
Linus found there still is a race in mremap after commit 5d1904204c99
("mremap: fix race between mremap() and page cleanning").As described by Linus:
"the issue is that another thread might make the pte be dirty (in the
hardware walker, so no locking of ours will make any difference)
*after* we checked whether it was dirty, but *before* we removed it
from the page tables"Fix it by moving the check after we removed it from the page table.
Suggested-by: Linus Torvalds
Signed-off-by: Aaron Lu
Signed-off-by: Linus Torvalds
18 Nov, 2016
1 commit
-
Prior to 3.15, there was a race between zap_pte_range() and
page_mkclean() where writes to a page could be lost. Dave Hansen
discovered by inspection that there is a similar race between
move_ptes() and page_mkclean().We've been able to reproduce the issue by enlarging the race window with
a msleep(), but have not been able to hit it without modifying the code.
So, we think it's a real issue, but is difficult or impossible to hit in
practice.The zap_pte_range() issue is fixed by commit 1cf35d47712d("mm: split
'tlb_flush_mmu()' into tlb flushing and memory freeing parts"). And
this patch is to fix the race between page_mkclean() and mremap().Here is one possible way to hit the race: suppose a process mmapped a
file with READ | WRITE and SHARED, it has two threads and they are bound
to 2 different CPUs, e.g. CPU1 and CPU2. mmap returned X, then thread
1 did a write to addr X so that CPU1 now has a writable TLB for addr X
on it. Thread 2 starts mremaping from addr X to Y while thread 1
cleaned the page and then did another write to the old addr X again.
The 2nd write from thread 1 could succeed but the value will get lost.thread 1 thread 2
(bound to CPU1) (bound to CPU2)1: write 1 to addr X to get a
writeable TLB on this CPU2: mremap starts
3: move_ptes emptied PTE for addr X
and setup new PTE for addr Y and
then dropped PTL for X and Y4: page laundering for N by doing
fadvise FADV_DONTNEED. When done,
pageframe N is deemed clean.5: *write 2 to addr X
6: tlb flush for addr X
7: munmap (Y, pagesize) to make the
page unmapped8: fadvise with FADV_DONTNEED again
to kick the page off the pagecache9: pread the page from file to verify
the value. If 1 is there, it means
we have lost the written 2.*the write may or may not cause segmentation fault, it depends on
if the TLB is still on the CPU.Please note that this is only one specific way of how the race could
occur, it didn't mean that the race could only occur in exact the above
config, e.g. more than 2 threads could be involved and fadvise() could
be done in another thread, etc.For anonymous pages, they could race between mremap() and page reclaim:
THP: a huge PMD is moved by mremap to a new huge PMD, then the new huge
PMD gets unmapped/splitted/pagedout before the flush tlb happened for
the old huge PMD in move_page_tables() and we could still write data to
it. The normal anonymous page has similar situation.To fix this, check for any dirty PTE in move_ptes()/move_huge_pmd() and
if any, did the flush before dropping the PTL. If we did the flush for
every move_ptes()/move_huge_pmd() call then we do not need to do the
flush in move_pages_tables() for the whole range. But if we didn't, we
still need to do the whole range flush.Alternatively, we can track which part of the range is flushed in
move_ptes()/move_huge_pmd() and which didn't to avoid flushing the whole
range in move_page_tables(). But that would require multiple tlb
flushes for the different sub-ranges and should be less efficient than
the single whole range flush.KBuild test on my Sandybridge desktop doesn't show any noticeable change.
v4.9-rc4:
real 5m14.048s
user 32m19.800s
sys 4m50.320sWith this commit:
real 5m13.888s
user 32m19.330s
sys 4m51.200sReported-by: Dave Hansen
Signed-off-by: Aaron Lu
Signed-off-by: Linus Torvalds
27 Jul, 2016
1 commit
-
split_huge_pmd() doesn't guarantee that the pmd is normal pmd pointing
to pte entries, which can be checked with pmd_trans_unstable(). Some
callers make this assertion and some do it differently and some not, so
let's do it in a unified manner.Link: http://lkml.kernel.org/r/1464741400-12143-1-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi
Cc: "Kirill A. Shutemov"
Cc: Hugh Dickins
Cc: Mel Gorman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
24 May, 2016
1 commit
-
This is a follow up work for oom_reaper [1]. As the async OOM killing
depends on oom_sem for read we would really appreciate if a holder for
write didn't stood in the way. This patchset is changing many of
down_write calls to be killable to help those cases when the writer is
blocked and waiting for readers to release the lock and so help
__oom_reap_task to process the oom victim.Most of the patches are really trivial because the lock is help from a
shallow syscall paths where we can return EINTR trivially and allow the
current task to die (note that EINTR will never get to the userspace as
the task has fatal signal pending). Others seem to be easy as well as
the callers are already handling fatal errors and bail and return to
userspace which should be sufficient to handle the failure gracefully.
I am not familiar with all those code paths so a deeper review is really
appreciated.As this work is touching more areas which are not directly connected I
have tried to keep the CC list as small as possible and people who I
believed would be familiar are CCed only to the specific patches (all
should have received the cover though).This patchset is based on linux-next and it depends on
down_write_killable for rw_semaphores which got merged into tip
locking/rwsem branch and it is merged into this next tree. I guess it
would be easiest to route these patches via mmotm because of the
dependency on the tip tree but if respective maintainers prefer other
way I have no objections.I haven't covered all the mmap_write(mm->mmap_sem) instances here
$ git grep "down_write(.*\)" next/master | wc -l
98
$ git grep "down_write(.*\)" | wc -l
62I have tried to cover those which should be relatively easy to review in
this series because this alone should be a nice improvement. Other
places can be changed on top.[0] http://lkml.kernel.org/r/1456752417-9626-1-git-send-email-mhocko@kernel.org
[1] http://lkml.kernel.org/r/1452094975-551-1-git-send-email-mhocko@kernel.org
[2] http://lkml.kernel.org/r/1456750705-7141-1-git-send-email-mhocko@kernel.orgThis patch (of 18):
This is the first step in making mmap_sem write waiters killable. It
focuses on the trivial ones which are taking the lock early after
entering the syscall and they are not changing state before.Therefore it is very easy to change them to use down_write_killable and
immediately return with -EINTR. This will allow the waiter to pass away
without blocking the mmap_sem which might be required to make a forward
progress. E.g. the oom reaper will need the lock for reading to
dismantle the OOM victim address space.The only tricky function in this patch is vm_mmap_pgoff which has many
call sites via vm_mmap. To reduce the risk keep vm_mmap with the
original non-killable semantic for now.vm_munmap callers do not bother checking the return value so open code
it into the munmap syscall path for now for simplicity.Signed-off-by: Michal Hocko
Acked-by: Vlastimil Babka
Cc: Mel Gorman
Cc: "Kirill A. Shutemov"
Cc: Konstantin Khlebnikov
Cc: Hugh Dickins
Cc: Andrea Arcangeli
Cc: David Rientjes
Cc: Dave Hansen
Cc: Johannes Weiner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
20 May, 2016
2 commits
-
Whatever huge pagecache implementation we go with, file rmap locking
must be added to anon rmap locking, when mremap's move_page_tables()
finds a pmd_trans_huge pmd entry: a simple change, let's do it now.Factor out take_rmap_locks() and drop_rmap_locks() to handle the locking
for make move_ptes() and move_page_tables(), and delete the
VM_BUG_ON_VMA which rejected vm_file and required anon_vma.Signed-off-by: Hugh Dickins
Cc: "Kirill A. Shutemov"
Cc: Andrea Arcangeli
Cc: Andres Lagar-Cavilla
Cc: Yang Shi
Cc: Ning Qu
Cc: Mel Gorman
Cc: Andres Lagar-Cavilla
Cc: Konstantin Khlebnikov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Remove move_huge_pmd()'s redundant new_vma arg: all it was used for was
a VM_NOHUGEPAGE check on new_vma flags, but the new_vma is cloned from
the old vma, so a trans_huge_pmd in the new_vma will be as acceptable as
it was in the old vma, alignment and size permitting.Signed-off-by: Hugh Dickins
Cc: "Kirill A. Shutemov"
Cc: Andrea Arcangeli
Cc: Andres Lagar-Cavilla
Cc: Yang Shi
Cc: Ning Qu
Cc: Mel Gorman
Cc: Andres Lagar-Cavilla
Cc: Konstantin Khlebnikov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
18 Mar, 2016
2 commits
-
There are few things about *pte_alloc*() helpers worth cleaning up:
- 'vma' argument is unused, let's drop it;
- most __pte_alloc() callers do speculative check for pmd_none(),
before taking ptl: let's introduce pte_alloc() macro which does
the check.The only direct user of __pte_alloc left is userfaultfd, which has
different expectation about atomicity wrt pmd.- pte_alloc_map() and pte_alloc_map_lock() are redefined using
pte_alloc().[sudeep.holla@arm.com: fix build for arm64 hugetlbpage]
[sfr@canb.auug.org.au: fix arch/arm/mm/mmu.c some more]
Signed-off-by: Kirill A. Shutemov
Cc: Dave Hansen
Signed-off-by: Sudeep Holla
Acked-by: Kirill A. Shutemov
Signed-off-by: Stephen Rothwell
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
max_map_count sysctl unrelated to scheduler. Move its bits from
include/linux/sched/sysctl.h to include/linux/mm.h.Signed-off-by: Andrey Ryabinin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
12 Feb, 2016
1 commit
-
DAX implements split_huge_pmd() by clearing pmd. This simple approach
reduces memory overhead, as we don't need to deposit page table on huge
page mapping to make split_huge_pmd() never-fail. PTE table can be
allocated and populated later on page fault from backing store.But one side effect is that have to check if pmd is pmd_none() after
split_huge_pmd(). In most places we do this already to deal with
parallel MADV_DONTNEED.But I found two call sites which is not affected by MADV_DONTNEED (due
down_write(mmap_sem)), but need to have the check to work with DAX
properly.Signed-off-by: Kirill A. Shutemov
Cc: Dan Williams
Cc: Matthew Wilcox
Cc: Andrea Arcangeli
Cc: Ross Zwisler
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 Jan, 2016
2 commits
-
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We are going to decouple splitting THP PMD from splitting underlying
compound page.This patch renames split_huge_page_pmd*() functions to split_huge_pmd*()
to reflect the fact that it doesn't imply page splitting, only PMD.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Acked-by: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
15 Jan, 2016
1 commit
-
When inspecting a vague code inside prctl(PR_SET_MM_MEM) call (which
testing the RLIMIT_DATA value to figure out if we're allowed to assign
new @start_brk, @brk, @start_data, @end_data from mm_struct) it's been
commited that RLIMIT_DATA in a form it's implemented now doesn't do
anything useful because most of user-space libraries use mmap() syscall
for dynamic memory allocations.Linus suggested to convert RLIMIT_DATA rlimit into something suitable
for anonymous memory accounting. But in this patch we go further, and
the changes are bundled together as:* keep vma counting if CONFIG_PROC_FS=n, will be used for limits
* replace mm->shared_vm with better defined mm->data_vm
* account anonymous executable areas as executable
* account file-backed growsdown/up areas as stack
* drop struct file* argument from vm_stat_account
* enforce RLIMIT_DATA for size of data areasThis way code looks cleaner: now code/stack/data classification depends
only on vm_flags state:VM_EXEC & ~VM_WRITE -> code (VmExe + VmLib in proc)
VM_GROWSUP | VM_GROWSDOWN -> stack (VmStk)
VM_WRITE & ~VM_SHARED & !stack -> data (VmData)The rest (VmSize - VmData - VmStk - VmExe - VmLib) could be called
"shared", but that might be strange beast like readonly-private or VM_IO
area.- RLIMIT_AS limits whole address space "VmSize"
- RLIMIT_STACK limits stack "VmStk" (but each vma individually)
- RLIMIT_DATA now limits "VmData"Signed-off-by: Konstantin Khlebnikov
Signed-off-by: Cyrill Gorcunov
Cc: Quentin Casasnovas
Cc: Vegard Nossum
Acked-by: Linus Torvalds
Cc: Willy Tarreau
Cc: Andy Lutomirski
Cc: Kees Cook
Cc: Vladimir Davydov
Cc: Pavel Emelyanov
Cc: Peter Zijlstra
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
05 Jan, 2016
1 commit
-
mremap() with MREMAP_FIXED on a VM_PFNMAP range causes the following
WARN_ON_ONCE() message in untrack_pfn().WARNING: CPU: 1 PID: 3493 at arch/x86/mm/pat.c:985 untrack_pfn+0xbd/0xd0()
Call Trace:
[] dump_stack+0x45/0x57
[] warn_slowpath_common+0x86/0xc0
[] warn_slowpath_null+0x1a/0x20
[] untrack_pfn+0xbd/0xd0
[] unmap_single_vma+0x80e/0x860
[] unmap_vmas+0x55/0xb0
[] unmap_region+0xac/0x120
[] do_munmap+0x28a/0x460
[] move_vma+0x1b3/0x2e0
[] SyS_mremap+0x3b3/0x510
[] entry_SYSCALL_64_fastpath+0x12/0x71MREMAP_FIXED moves a pfnmap from old vma to new vma. untrack_pfn() is
called with the old vma after its pfnmap page table has been removed,
which causes follow_phys() to fail. The new vma has a new pfnmap to
the same pfn & cache type with VM_PAT set. Therefore, we only need to
clear VM_PAT from the old vma in this case.Add untrack_pfn_moved(), which clears VM_PAT from a given old vma.
move_vma() is changed to call this function with the old vma when
VM_PFNMAP is set. move_vma() then calls do_munmap(), and untrack_pfn()
is a no-op since VM_PAT is cleared.Reported-by: Stas Sergeev
Signed-off-by: Toshi Kani
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: H. Peter Anvin
Cc: Borislav Petkov
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1450832064-10093-2-git-send-email-toshi.kani@hpe.com
Signed-off-by: Thomas Gleixner
06 Nov, 2015
1 commit
-
linux/mm.h provides offset_in_page() macro. Let's use already predefined
macro instead of (addr & ~PAGE_MASK).Signed-off-by: Alexander Kuleshov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
05 Sep, 2015
4 commits
-
Minor, but this check is overcomplicated. Two half-intervals do NOT
overlap if END1
Acked-by: David Rientjes
Cc: Benjamin LaHaise
Cc: Hugh Dickins
Cc: Jeff Moyer
Cc: Kirill A. Shutemov
Cc: Laurent Dufour
Cc: Pavel Emelyanov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The "new_len > old_len" branch in vma_to_resize() looks very confusing.
It only covers the VM_DONTEXPAND/pgoff checks but everything below is
equally unneeded if new_len == old_len.Change this code to return if "new_len == old_len", new_len < old_len is
not possible, otherwise the code below is wrong anyway.Signed-off-by: Oleg Nesterov
Acked-by: David Rientjes
Cc: Benjamin LaHaise
Cc: Hugh Dickins
Cc: Jeff Moyer
Cc: Kirill A. Shutemov
Cc: Laurent Dufour
Cc: Pavel Emelyanov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
move_vma() sets *locked even if move_page_tables() or ->mremap() fails,
change sys_mremap() to check "ret & ~PAGE_MASK".I think we should simply remove the VM_LOCKED code in move_vma(), that is
why this patch doesn't change move_vma(). But this needs more cleanups.Signed-off-by: Oleg Nesterov
Acked-by: David Rientjes
Cc: Benjamin LaHaise
Cc: Hugh Dickins
Cc: Jeff Moyer
Cc: Kirill A. Shutemov
Cc: Laurent Dufour
Cc: Pavel Emelyanov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
vma->vm_ops->mremap() looks more natural and clean in move_vma(), and this
way ->mremap() can have more users. Say, vdso.While at it, s/aio_ring_remap/aio_ring_mremap/.
Note: this is the minimal change before ->mremap() finds another user in
file_operations; this method should have more arguments, and it can be
used to kill arch_remap().Signed-off-by: Oleg Nesterov
Acked-by: Pavel Emelyanov
Acked-by: Kirill A. Shutemov
Cc: David Rientjes
Cc: Benjamin LaHaise
Cc: Hugh Dickins
Cc: Jeff Moyer
Cc: Laurent Dufour
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
