Doug / smarc-fsl-linux-kernel

02 May, 2013

1 commit

  • 60bc851ae   af_unix: fix a fatal race with bit fields ... Browse Code »

    Using bit fields is dangerous on ppc64/sparc64, as the compiler [1]
    uses 64bit instructions to manipulate them.
    If the 64bit word includes any atomic_t or spinlock_t, we can lose
    critical concurrent changes.

    This is happening in af_unix, where unix_sk(sk)->gc_candidate/
    gc_maybe_cycle/lock share the same 64bit word.

    This leads to fatal deadlock, as one/several cpus spin forever
    on a spinlock that will never be available again.

    A safer way would be to use a long to store flags.
    This way we are sure compiler/arch wont do bad things.

    As we own unix_gc_lock spinlock when clearing or setting bits,
    we can use the non atomic __set_bit()/__clear_bit().

    recursion_level can share the same 64bit location with the spinlock,
    as it is set only with this spinlock held.

    [1] bug fixed in gcc-4.8.0 :
    http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52080

    Reported-by: Ambrose Feinstein
    Signed-off-by: Eric Dumazet
    Cc: Benjamin Herrenschmidt
    Cc: Paul Mackerras
    Signed-off-by: David S. Miller

    Eric Dumazet
     

30 Apr, 2013

2 commits

23 Apr, 2013

1 commit

  • 6e0895c2e   Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net ... Browse Code »

    Conflicts:
    drivers/net/ethernet/emulex/benet/be_main.c
    drivers/net/ethernet/intel/igb/igb_main.c
    drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
    include/net/scm.h
    net/batman-adv/routing.c
    net/ipv4/tcp_input.c

    The e{uid,gid} --> {uid,gid} credentials fix conflicted with the
    cleanup in net-next to now pass cred structs around.

    The be2net driver had a bug fix in 'net' that overlapped with the VLAN
    interface changes by Patrick McHardy in net-next.

    An IGB conflict existed because in 'net' the build_skb() support was
    reverted, and in 'net-next' there was a comment style fix within that
    code.

    Several batman-adv conflicts were resolved by making sure that all
    calls to batadv_is_my_mac() are changed to have a new bat_priv first
    argument.

    Eric Dumazet's TS ECR fix in TCP in 'net' conflicted with the F-RTO
    rewrite in 'net-next', mostly overlapping changes.

    Thanks to Stephen Rothwell and Antonio Quartulli for help with several
    of these merge resolutions.

    Signed-off-by: David S. Miller

    David S. Miller
     

08 Apr, 2013

2 commits

  • 6b0ee8c03   scm: Stop passing struct cred ... Browse Code »

    Now that uids and gids are completely encapsulated in kuid_t
    and kgid_t we no longer need to pass struct cred which allowed
    us to test both the uid and the user namespace for equality.

    Passing struct cred potentially allows us to pass the entire group
    list as BSD does but I don't believe the cost of cache line misses
    justifies retaining code for a future potential application.

    Signed-off-by: "Eric W. Biederman"
    Signed-off-by: David S. Miller

    Eric W. Biederman
     
  • d978a6361   Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net ... Browse Code »

    Conflicts:
    drivers/nfc/microread/mei.c
    net/netfilter/nfnetlink_queue_core.c

    Pull in 'net' to get Eric Biederman's AF_UNIX fix, upon which
    some cleanups are going to go on-top.

    Signed-off-by: David S. Miller

    David S. Miller
     

05 Apr, 2013

2 commits

  • 0e82e7f6d   af_unix: If we don't care about credentials coallesce all messages ... Browse Code »

    It was reported that the following LSB test case failed
    https://lsbbugs.linuxfoundation.org/attachment.cgi?id=2144 because we
    were not coallescing unix stream messages when the application was
    expecting us to.

    The problem was that the first send was before the socket was accepted
    and thus sock->sk_socket was NULL in maybe_add_creds, and the second
    send after the socket was accepted had a non-NULL value for sk->socket
    and thus we could tell the credentials were not needed so we did not
    bother.

    The unnecessary credentials on the first message cause
    unix_stream_recvmsg to start verifying that all messages had the same
    credentials before coallescing and then the coallescing failed because
    the second message had no credentials.

    Ignoring credentials when we don't care in unix_stream_recvmsg fixes a
    long standing pessimization which would fail to coallesce messages when
    reading from a unix stream socket if the senders were different even if
    we did not care about their credentials.

    I have tested this and verified that the in the LSB test case mentioned
    above that the messages do coallesce now, while the were failing to
    coallesce without this change.

    Reported-by: Karel Srot
    Reported-by: Ding Tianhong
    Signed-off-by: "Eric W. Biederman"
    Signed-off-by: David S. Miller

    Eric W. Biederman
     
  • 25da0e3e9   Revert "af_unix: dont send SCM_CREDENTIAL when dest socket is NULL" ... Browse Code »

    This reverts commit 14134f6584212d585b310ce95428014b653dfaf6.

    The problem that the above patch was meant to address is that af_unix
    messages are not being coallesced because we are sending unnecesarry
    credentials. Not sending credentials in maybe_add_creds totally
    breaks unconnected unix domain sockets that wish to send credentails
    to other sockets.

    In practice this break some versions of udev because they receive a
    message and the sending uid is bogus so they drop the message.

    Reported-by: Sven Joachim
    Signed-off-by: "Eric W. Biederman"
    Signed-off-by: David S. Miller

    Eric W. Biederman
     

03 Apr, 2013

1 commit

  • 8facd5fb7   net: fix smatch warnings inside datagram_poll ... Browse Code »

    Commit 7d4c04fc170087119727119074e72445f2bb192b ("net: add option to enable
    error queue packets waking select") has an issue due to operator precedence
    causing the bit-wise OR to bind to the sock_flags call instead of the result of
    the terniary conditional. This fixes the *_poll functions to work properly. The
    old code results in "mask |= POLLPRI" instead of what was intended, which is to
    only include POLLPRI when the socket option is enabled.

    Signed-off-by: Jacob Keller
    Signed-off-by: David S. Miller

    Jacob Keller
     

01 Apr, 2013

1 commit

  • 7d4c04fc1   net: add option to enable error queue packets waking select ... Browse Code »

    Currently, when a socket receives something on the error queue it only wakes up
    the socket on select if it is in the "read" list, that is the socket has
    something to read. It is useful also to wake the socket if it is in the error
    list, which would enable software to wait on error queue packets without waking
    up for regular data on the socket. The main use case is for receiving
    timestamped transmit packets which return the timestamp to the socket via the
    error queue. This enables an application to select on the socket for the error
    queue only instead of for the regular traffic.

    -v2-
    * Added the SO_SELECT_ERR_QUEUE socket option to every architechture specific file
    * Modified every socket poll function that checks error queue

    Signed-off-by: Jacob Keller
    Cc: Jeffrey Kirsher
    Cc: Richard Cochran
    Cc: Matthew Vick
    Signed-off-by: David S. Miller

    Keller, Jacob E
     

27 Mar, 2013

1 commit

  • 14134f658   af_unix: dont send SCM_CREDENTIAL when dest socket is NULL ... Browse Code »

    SCM_SCREDENTIALS should apply to write() syscalls only either source or destination
    socket asserted SOCK_PASSCRED. The original implememtation in maybe_add_creds is wrong,
    and breaks several LSB testcases ( i.e. /tset/LSB.os/netowkr/recvfrom/T.recvfrom).

    Origionally-authored-by: Karel Srot
    Signed-off-by: Ding Tianhong
    Acked-by: Eric Dumazet
    Signed-off-by: David S. Miller

    dingtianhong
     

26 Mar, 2013

1 commit

  • ded34e0fe   unix: fix a race condition in unix_release() ... Browse Code »

    As reported by Jan, and others over the past few years, there is a
    race condition caused by unix_release setting the sock->sk pointer
    to NULL before properly marking the socket as dead/orphaned. This
    can cause a problem with the LSM hook security_unix_may_send() if
    there is another socket attempting to write to this partially
    released socket in between when sock->sk is set to NULL and it is
    marked as dead/orphaned. This patch fixes this by only setting
    sock->sk to NULL after the socket has been marked as dead; I also
    take the opportunity to make unix_release_sock() a void function
    as it only ever returned 0/success.

    Dave, I think this one should go on the -stable pile.

    Special thanks to Jan for coming up with a reproducer for this
    problem.

    Reported-by: Jan Stancek
    Signed-off-by: Paul Moore
    Signed-off-by: David S. Miller

    Paul Moore
     

28 Feb, 2013

1 commit

  • b67bfe0d4   hlist: drop the node parameter from iterators ... Browse Code »

    I'm not sure why, but the hlist for each entry iterators were conceived

    list_for_each_entry(pos, head, member)

    The hlist ones were greedy and wanted an extra parameter:

    hlist_for_each_entry(tpos, pos, head, member)

    Why did they need an extra pos parameter? I'm not quite sure. Not only
    they don't really need it, it also prevents the iterator from looking
    exactly like the list iterator, which is unfortunate.

    Besides the semantic patch, there was some manual work required:

    - Fix up the actual hlist iterators in linux/list.h
    - Fix up the declaration of other iterators based on the hlist ones.
    - A very small amount of places were using the 'node' parameter, this
    was modified to use 'obj->member' instead.
    - Coccinelle didn't handle the hlist_for_each_entry_safe iterator
    properly, so those had to be fixed up manually.

    The semantic patch which is mostly the work of Peter Senna Tschudin is here:

    @@
    iterator name hlist_for_each_entry, hlist_for_each_entry_continue, hlist_for_each_entry_from, hlist_for_each_entry_rcu, hlist_for_each_entry_rcu_bh, hlist_for_each_entry_continue_rcu_bh, for_each_busy_worker, ax25_uid_for_each, ax25_for_each, inet_bind_bucket_for_each, sctp_for_each_hentry, sk_for_each, sk_for_each_rcu, sk_for_each_from, sk_for_each_safe, sk_for_each_bound, hlist_for_each_entry_safe, hlist_for_each_entry_continue_rcu, nr_neigh_for_each, nr_neigh_for_each_safe, nr_node_for_each, nr_node_for_each_safe, for_each_gfn_indirect_valid_sp, for_each_gfn_sp, for_each_host;

    type T;
    expression a,c,d,e;
    identifier b;
    statement S;
    @@

    -T b;

    [akpm@linux-foundation.org: drop bogus change from net/ipv4/raw.c]
    [akpm@linux-foundation.org: drop bogus hunk from net/ipv6/raw.c]
    [akpm@linux-foundation.org: checkpatch fixes]
    [akpm@linux-foundation.org: fix warnings]
    [akpm@linux-foudnation.org: redo intrusive kvm changes]
    Tested-by: Peter Senna Tschudin
    Acked-by: Paul E. McKenney
    Signed-off-by: Sasha Levin
    Cc: Wu Fengguang
    Cc: Marcelo Tosatti
    Cc: Gleb Natapov
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Sasha Levin
     

27 Feb, 2013

1 commit

  • d895cb1af   Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs ... Browse Code »

    Pull vfs pile (part one) from Al Viro:
    "Assorted stuff - cleaning namei.c up a bit, fixing ->d_name/->d_parent
    locking violations, etc.

    The most visible changes here are death of FS_REVAL_DOT (replaced with
    "has ->d_weak_revalidate()") and a new helper getting from struct file
    to inode. Some bits of preparation to xattr method interface changes.

    Misc patches by various people sent this cycle *and* ocfs2 fixes from
    several cycles ago that should've been upstream right then.

    PS: the next vfs pile will be xattr stuff."

    * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (46 commits)
    saner proc_get_inode() calling conventions
    proc: avoid extra pde_put() in proc_fill_super()
    fs: change return values from -EACCES to -EPERM
    fs/exec.c: make bprm_mm_init() static
    ocfs2/dlm: use GFP_ATOMIC inside a spin_lock
    ocfs2: fix possible use-after-free with AIO
    ocfs2: Fix oops in ocfs2_fast_symlink_readpage() code path
    get_empty_filp()/alloc_file() leave both ->f_pos and ->f_version zero
    target: writev() on single-element vector is pointless
    export kernel_write(), convert open-coded instances
    fs: encode_fh: return FILEID_INVALID if invalid fid_type
    kill f_vfsmnt
    vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op
    nfsd: handle vfs_getattr errors in acl protocol
    switch vfs_getattr() to struct path
    default SET_PERSONALITY() in linux/elf.h
    ceph: prepopulate inodes only when request is aborted
    d_hash_and_lookup(): export, switch open-coded instances
    9p: switch v9fs_set_create_acl() to inode+fid, do it before d_instantiate()
    9p: split dropping the acls from v9fs_set_create_acl()
    ...

    Linus Torvalds
     

23 Feb, 2013

1 commit

19 Feb, 2013

2 commits

  • ece31ffd5   net: proc: change proc_net_remove to remove_proc_entry ... Browse Code »

    proc_net_remove is only used to remove proc entries
    that under /proc/net,it's not a general function for
    removing proc entries of netns. if we want to remove
    some proc entries which under /proc/net/stat/, we still
    need to call remove_proc_entry.

    this patch use remove_proc_entry to replace proc_net_remove.
    we can remove proc_net_remove after this patch.

    Signed-off-by: Gao feng
    Signed-off-by: David S. Miller

    Gao feng
     
  • d4beaa66a   net: proc: change proc_net_fops_create to proc_create ... Browse Code »

    Right now, some modules such as bonding use proc_create
    to create proc entries under /proc/net/, and other modules
    such as ipv4 use proc_net_fops_create.

    It looks a little chaos.this patch changes all of
    proc_net_fops_create to proc_create. we can remove
    proc_net_fops_create after this patch.

    Signed-off-by: Gao feng
    Signed-off-by: David S. Miller

    Gao feng
     

10 Jan, 2013

1 commit

19 Nov, 2012

1 commit

  • 464dc801c   net: Don't export sysctls to unprivileged users ... Browse Code »

    In preparation for supporting the creation of network namespaces
    by unprivileged users, modify all of the per net sysctl exports
    and refuse to allow them to unprivileged users.

    This makes it safe for unprivileged users in general to access
    per net sysctls, and allows sysctls to be exported to unprivileged
    users on an individual basis as they are deemed safe.

    Signed-off-by: "Eric W. Biederman"
    Signed-off-by: David S. Miller

    Eric W. Biederman
     

24 Oct, 2012

1 commit

18 Sep, 2012

1 commit

11 Sep, 2012

1 commit

  • 15e473046   netlink: Rename pid to portid to avoid confusion ... Browse Code »

    It is a frequent mistake to confuse the netlink port identifier with a
    process identifier. Try to reduce this confusion by renaming fields
    that hold port identifiers portid instead of pid.

    I have carefully avoided changing the structures exported to
    userspace to avoid changing the userspace API.

    I have successfully built an allyesconfig kernel with this change.

    Signed-off-by: "Eric W. Biederman"
    Acked-by: Stephen Hemminger
    Signed-off-by: David S. Miller

    Eric W. Biederman
     

01 Sep, 2012

1 commit

22 Aug, 2012

1 commit

  • e0e3cea46   af_netlink: force credentials passing [CVE-2012-3520] ... Browse Code »

    Pablo Neira Ayuso discovered that avahi and
    potentially NetworkManager accept spoofed Netlink messages because of a
    kernel bug. The kernel passes all-zero SCM_CREDENTIALS ancillary data
    to the receiver if the sender did not provide such data, instead of not
    including any such data at all or including the correct data from the
    peer (as it is the case with AF_UNIX).

    This bug was introduced in commit 16e572626961
    (af_unix: dont send SCM_CREDENTIALS by default)

    This patch forces passing credentials for netlink, as
    before the regression.

    Another fix would be to not add SCM_CREDENTIALS in
    netlink messages if not provided by the sender, but it
    might break some programs.

    With help from Florian Weimer & Petr Matousek

    This issue is designated as CVE-2012-3520

    Signed-off-by: Eric Dumazet
    Cc: Petr Matousek
    Cc: Florian Weimer
    Cc: Pablo Neira Ayuso
    Signed-off-by: David S. Miller

    Eric Dumazet
     

02 Aug, 2012

1 commit

  • a0e881b7c   Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs ... Browse Code »

    Pull second vfs pile from Al Viro:
    "The stuff in there: fsfreeze deadlock fixes by Jan (essentially, the
    deadlock reproduced by xfstests 068), symlink and hardlink restriction
    patches, plus assorted cleanups and fixes.

    Note that another fsfreeze deadlock (emergency thaw one) is *not*
    dealt with - the series by Fernando conflicts a lot with Jan's, breaks
    userland ABI (FIFREEZE semantics gets changed) and trades the deadlock
    for massive vfsmount leak; this is going to be handled next cycle.
    There probably will be another pull request, but that stuff won't be
    in it."

    Fix up trivial conflicts due to unrelated changes next to each other in
    drivers/{staging/gdm72xx/usb_boot.c, usb/gadget/storage_common.c}

    * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (54 commits)
    delousing target_core_file a bit
    Documentation: Correct s_umount state for freeze_fs/unfreeze_fs
    fs: Remove old freezing mechanism
    ext2: Implement freezing
    btrfs: Convert to new freezing mechanism
    nilfs2: Convert to new freezing mechanism
    ntfs: Convert to new freezing mechanism
    fuse: Convert to new freezing mechanism
    gfs2: Convert to new freezing mechanism
    ocfs2: Convert to new freezing mechanism
    xfs: Convert to new freezing code
    ext4: Convert to new freezing mechanism
    fs: Protect write paths by sb_start_write - sb_end_write
    fs: Skip atime update on frozen filesystem
    fs: Add freezing handling to mnt_want_write() / mnt_drop_write()
    fs: Improve filesystem freezing handling
    switch the protection of percpu_counter list to spinlock
    nfsd: Push mnt_want_write() outside of i_mutex
    btrfs: Push mnt_want_write() outside of i_mutex
    fat: Push mnt_want_write() outside of i_mutex
    ...

    Linus Torvalds
     

30 Jul, 2012

3 commits

17 Jul, 2012

1 commit

  • 51d7cccf0   net: make sock diag per-namespace ... Browse Code »

    Before this patch sock_diag works for init_net only and dumps
    information about sockets from all namespaces.

    This patch expands sock_diag for all name-spaces.
    It creates a netlink kernel socket for each netns and filters
    data during dumping.

    v2: filter accoding with netns in all places
    remove an unused variable.

    Cc: "David S. Miller"
    Cc: Alexey Kuznetsov
    Cc: James Morris
    Cc: Hideaki YOSHIFUJI
    Cc: Patrick McHardy
    Cc: Pavel Emelyanov
    CC: Eric Dumazet
    Cc: linux-kernel@vger.kernel.org
    Cc: netdev@vger.kernel.org
    Signed-off-by: Andrew Vagin
    Acked-by: Pavel Emelyanov
    Signed-off-by: David S. Miller

    Andrey Vagin
     

28 Jun, 2012

1 commit

27 Jun, 2012

1 commit

10 Jun, 2012

1 commit

  • 8b51b064a   af_unix: remove unix_iter_state ... Browse Code »

    As pointed out by Michael Tokarev , struct unix_iter_state is no longer
    needed.

    Suggested-by: Michael Tokarev
    Signed-off-by: Eric Dumazet
    Cc: Steven Whitehouse
    Cc: Pavel Emelyanov
    Signed-off-by: David S. Miller

    Eric Dumazet
     

09 Jun, 2012

1 commit

  • 7123aaa3a   af_unix: speedup /proc/net/unix ... Browse Code »

    /proc/net/unix has quadratic behavior, and can hold unix_table_lock for
    a while if high number of unix sockets are alive. (90 ms for 200k
    sockets...)

    We already have a hash table, so its quite easy to use it.

    Problem is unbound sockets are still hashed in a single hash slot
    (unix_socket_table[UNIX_HASH_TABLE])

    This patch also spreads unbound sockets to 256 hash slots, to speedup
    both /proc/net/unix and unix_diag.

    Time to read /proc/net/unix with 200k unix sockets :
    (time dd if=/proc/net/unix of=/dev/null bs=4k)

    before : 520 secs
    after : 2 secs

    Signed-off-by: Eric Dumazet
    Cc: Steven Whitehouse
    Cc: Pavel Emelyanov
    Signed-off-by: David S. Miller

    Eric Dumazet
     

26 Apr, 2012

1 commit

21 Apr, 2012

2 commits

  • ec8f23ce0   net: Convert all sysctl registrations to register_net_sysctl ... Browse Code »

    This results in code with less boiler plate that is a bit easier
    to read.

    Additionally stops us from using compatibility code in the sysctl
    core, hastening the day when the compatibility code can be removed.

    Signed-off-by: Eric W. Biederman
    Acked-by: Pavel Emelyanov
    Signed-off-by: David S. Miller

    Eric W. Biederman
     
  • 5dd3df105   net: Move all of the network sysctls without a namespace into init_net. ... Browse Code »

    This makes it clearer which sysctls are relative to your current network
    namespace.

    This makes it a little less error prone by not exposing sysctls for the
    initial network namespace in other namespaces.

    This is the same way we handle all of our other network interfaces to
    userspace and I can't honestly remember why we didn't do this for
    sysctls right from the start.

    Signed-off-by: Eric W. Biederman
    Acked-by: Pavel Emelyanov
    Signed-off-by: David S. Miller

    Eric W. Biederman
     

16 Apr, 2012

1 commit

04 Apr, 2012

1 commit

  • eb6a24816   af_unix: reduce high order page allocations ... Browse Code »

    unix_dgram_sendmsg() currently builds linear skbs, and this can stress
    page allocator with high order page allocations. When memory gets
    fragmented, this can eventually fail.

    We can try to use order-2 allocations for skb head (SKB_MAX_ALLOC) plus
    up to 16 page fragments to lower pressure on buddy allocator.

    This patch has no effect on messages of less than 16064 bytes.
    (on 64bit arches with PAGE_SIZE=4096)

    For bigger messages (from 16065 to 81600 bytes), this patch brings
    reliability at the expense of performance penalty because of extra pages
    allocations.

    netperf -t DG_STREAM -T 0,2 -- -m 16064 -s 200000
    ->4086040 Messages / 10s

    netperf -t DG_STREAM -T 0,2 -- -m 16068 -s 200000
    ->3901747 Messages / 10s

    Signed-off-by: Eric Dumazet
    Signed-off-by: David S. Miller

    Eric Dumazet
     

24 Mar, 2012

1 commit

  • 626cf2366   poll: add poll_requested_events() and poll_does_not_wait() functions ... Browse Code »

    In some cases the poll() implementation in a driver has to do different
    things depending on the events the caller wants to poll for. An example
    is when a driver needs to start a DMA engine if the caller polls for
    POLLIN, but doesn't want to do that if POLLIN is not requested but instead
    only POLLOUT or POLLPRI is requested. This is something that can happen
    in the video4linux subsystem among others.

    Unfortunately, the current epoll/poll/select implementation doesn't
    provide that information reliably. The poll_table_struct does have it: it
    has a key field with the event mask. But once a poll() call matches one
    or more bits of that mask any following poll() calls are passed a NULL
    poll_table pointer.

    Also, the eventpoll implementation always left the key field at ~0 instead
    of using the requested events mask.

    This was changed in eventpoll.c so the key field now contains the actual
    events that should be polled for as set by the caller.

    The solution to the NULL poll_table pointer is to set the qproc field to
    NULL in poll_table once poll() matches the events, not the poll_table
    pointer itself. That way drivers can obtain the mask through a new
    poll_requested_events inline.

    The poll_table_struct can still be NULL since some kernel code calls it
    internally (netfs_state_poll() in ./drivers/staging/pohmelfs/netfs.h). In
    that case poll_requested_events() returns ~0 (i.e. all events).

    Very rarely drivers might want to know whether poll_wait will actually
    wait. If another earlier file descriptor in the set already matched the
    events the caller wanted to wait for, then the kernel will return from the
    select() call without waiting. This might be useful information in order
    to avoid doing expensive work.

    A new helper function poll_does_not_wait() is added that drivers can use
    to detect this situation. This is now used in sock_poll_wait() in
    include/net/sock.h. This was the only place in the kernel that needed
    this information.

    Drivers should no longer access any of the poll_table internals, but use
    the poll_requested_events() and poll_does_not_wait() access functions
    instead. In order to enforce that the poll_table fields are now prepended
    with an underscore and a comment was added warning against using them
    directly.

    This required a change in unix_dgram_poll() in unix/af_unix.c which used
    the key field to get the requested events. It's been replaced by a call
    to poll_requested_events().

    For qproc it was especially important to change its name since the
    behavior of that field changes with this patch since this function pointer
    can now be NULL when that wasn't possible in the past.

    Any driver accessing the qproc or key fields directly will now fail to compile.

    Some notes regarding the correctness of this patch: the driver's poll()
    function is called with a 'struct poll_table_struct *wait' argument. This
    pointer may or may not be NULL, drivers can never rely on it being one or
    the other as that depends on whether or not an earlier file descriptor in
    the select()'s fdset matched the requested events.

    There are only three things a driver can do with the wait argument:

    1) obtain the key field:

    events = wait ? wait->key : ~0;

    This will still work although it should be replaced with the new
    poll_requested_events() function (which does exactly the same).
    This will now even work better, since wait is no longer set to NULL
    unnecessarily.

    2) use the qproc callback. This could be deadly since qproc can now be
    NULL. Renaming qproc should prevent this from happening. There are no
    kernel drivers that actually access this callback directly, BTW.

    3) test whether wait == NULL to determine whether poll would return without
    waiting. This is no longer sufficient as the correct test is now
    wait == NULL || wait->_qproc == NULL.

    However, the worst that can happen here is a slight performance hit in
    the case where wait != NULL and wait->_qproc == NULL. In that case the
    driver will assume that poll_wait() will actually add the fd to the set
    of waiting file descriptors. Of course, poll_wait() will not do that
    since it tests for wait->_qproc. This will not break anything, though.

    There is only one place in the whole kernel where this happens
    (sock_poll_wait() in include/net/sock.h) and that code will be replaced
    by a call to poll_does_not_wait() in the next patch.

    Note that even if wait->_qproc != NULL drivers cannot rely on poll_wait()
    actually waiting. The next file descriptor from the set might match the
    event mask and thus any possible waits will never happen.

    Signed-off-by: Hans Verkuil
    Reviewed-by: Jonathan Corbet
    Reviewed-by: Al Viro
    Cc: Davide Libenzi
    Signed-off-by: Hans de Goede
    Cc: Mauro Carvalho Chehab
    Cc: David Miller
    Cc: Eric Dumazet
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Hans Verkuil
     

22 Mar, 2012

1 commit

  • e2a0883e4   Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs ... Browse Code »

    Pull vfs pile 1 from Al Viro:
    "This is _not_ all; in particular, Miklos' and Jan's stuff is not there
    yet."

    * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (64 commits)
    ext4: initialization of ext4_li_mtx needs to be done earlier
    debugfs-related mode_t whack-a-mole
    hfsplus: add an ioctl to bless files
    hfsplus: change finder_info to u32
    hfsplus: initialise userflags
    qnx4: new helper - try_extent()
    qnx4: get rid of qnx4_bread/qnx4_getblk
    take removal of PF_FORKNOEXEC to flush_old_exec()
    trim includes in inode.c
    um: uml_dup_mmap() relies on ->mmap_sem being held, but activate_mm() doesn't hold it
    um: embed ->stub_pages[] into mmu_context
    gadgetfs: list_for_each_safe() misuse
    ocfs2: fix leaks on failure exits in module_init
    ecryptfs: make register_filesystem() the last potential failure exit
    ntfs: forgets to unregister sysctls on register_filesystem() failure
    logfs: missing cleanup on register_filesystem() failure
    jfs: mising cleanup on register_filesystem() failure
    make configfs_pin_fs() return root dentry on success
    configfs: configfs_create_dir() has parent dentry in dentry->d_parent
    configfs: sanitize configfs_create()
    ...

    Linus Torvalds