06 May, 2015
1 commit
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The documentation shows a need for gcc > 4.9.2, but it's really >=. The
Kconfig entries don't show require versions so add them. Correct a
latter/later typo too. Also mention that gcc 5 required to catch out of
bounds accesses to global and stack variables.Signed-off-by: Joe Perches
Signed-off-by: Andrey Ryabinin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
14 Feb, 2015
2 commits
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This feature let us to detect accesses out of bounds of global variables.
This will work as for globals in kernel image, so for globals in modules.
Currently this won't work for symbols in user-specified sections (e.g.
__init, __read_mostly, ...)The idea of this is simple. Compiler increases each global variable by
redzone size and add constructors invoking __asan_register_globals()
function. Information about global variable (address, size, size with
redzone ...) passed to __asan_register_globals() so we could poison
variable's redzone.This patch also forces module_alloc() to return 8*PAGE_SIZE aligned
address making shadow memory handling (
kasan_module_alloc()/kasan_module_free() ) more simple. Such alignment
guarantees that each shadow page backing modules address space correspond
to only one module_alloc() allocation.Signed-off-by: Andrey Ryabinin
Cc: Dmitry Vyukov
Cc: Konstantin Serebryany
Cc: Dmitry Chernenkov
Signed-off-by: Andrey Konovalov
Cc: Yuri Gribov
Cc: Konstantin Khlebnikov
Cc: Sasha Levin
Cc: Christoph Lameter
Cc: Joonsoo Kim
Cc: Dave Hansen
Cc: Andi Kleen
Cc: Ingo Molnar
Cc: Thomas Gleixner
Cc: "H. Peter Anvin"
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Kernel Address sanitizer (KASan) is a dynamic memory error detector. It
provides fast and comprehensive solution for finding use-after-free and
out-of-bounds bugs.KASAN uses compile-time instrumentation for checking every memory access,
therefore GCC > v4.9.2 required. v4.9.2 almost works, but has issues with
putting symbol aliases into the wrong section, which breaks kasan
instrumentation of globals.This patch only adds infrastructure for kernel address sanitizer. It's
not available for use yet. The idea and some code was borrowed from [1].Basic idea:
The main idea of KASAN is to use shadow memory to record whether each byte
of memory is safe to access or not, and use compiler's instrumentation to
check the shadow memory on each memory access.Address sanitizer uses 1/8 of the memory addressable in kernel for shadow
memory and uses direct mapping with a scale and offset to translate a
memory address to its corresponding shadow address.Here is function to translate address to corresponding shadow address:
unsigned long kasan_mem_to_shadow(unsigned long addr)
{
return (addr >> KASAN_SHADOW_SCALE_SHIFT) + KASAN_SHADOW_OFFSET;
}where KASAN_SHADOW_SCALE_SHIFT = 3.
So for every 8 bytes there is one corresponding byte of shadow memory.
The following encoding used for each shadow byte: 0 means that all 8 bytes
of the corresponding memory region are valid for access; k (1
Acked-by: Michal Marek
Signed-off-by: Andrey Konovalov
Cc: Dmitry Vyukov
Cc: Konstantin Serebryany
Cc: Dmitry Chernenkov
Cc: Yuri Gribov
Cc: Konstantin Khlebnikov
Cc: Sasha Levin
Cc: Christoph Lameter
Cc: Joonsoo Kim
Cc: Dave Hansen
Cc: Andi Kleen
Cc: Ingo Molnar
Cc: Thomas Gleixner
Cc: "H. Peter Anvin"
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Stephen Rothwell
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
