]> git.baikalelectronics.ru Git - kernel.git/commit
lib/idr.c: fix out-of-bounds pointer dereference
authorAndrey Ryabinin <a.ryabinin@samsung.com>
Fri, 8 Aug 2014 21:22:07 +0000 (14:22 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 8 Aug 2014 22:57:24 +0000 (15:57 -0700)
commit13caf1d0ac79ae7661f832c2dcd2a5c34ad6a16d
treed7f8872fd8e21b4ad301bda4de482ef41014c480
parentb1fe868dc7f75f4d670a0d3e24333d7defbc8e9a
lib/idr.c: fix out-of-bounds pointer dereference

I'm working on address sanitizer project for kernel.  Recently we
started experiments with stack instrumentation, to detect out-of-bounds
read/write bugs on stack.

Just after booting I've hit out-of-bounds read on stack in idr_for_each
(and in __idr_remove_all as well):

struct idr_layer **paa = &pa[0];

while (id >= 0 && id <= max) {
...
while (n < fls(id)) {
n += IDR_BITS;
p = *--paa; <--- here we are reading pa[-1] value.
}
}

Despite the fact that after this dereference we are exiting out of loop
and never use p, such behaviour is undefined and should be avoided.

Fix this by moving pointer derference to the beggining of the loop,
right before we will use it.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Alexey Preobrazhensky <preobr@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/idr.c