]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
proc: fix /proc/*/map_files lookup
authorAlexey Dobriyan <adobriyan@gmail.com>
Tue, 6 Feb 2018 23:36:59 +0000 (15:36 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 7 Feb 2018 02:32:43 +0000 (18:32 -0800)
commitac7f1061c2c11bb8936b1b6a94cdb48de732f7a4
tree1d01b6071cad203ecc73be49c817ef194381388a
parent9f7118b2007d5e7c7a061550d2ca2ecb841537dc
proc: fix /proc/*/map_files lookup

Current code does:

if (sscanf(dentry->d_name.name, "%lx-%lx", start, end) != 2)

However sscanf() is broken garbage.

It silently accepts whitespace between format specifiers
(did you know that?).

It silently accepts valid strings which result in integer overflow.

Do not use sscanf() for any even remotely reliable parsing code.

OK
# readlink '/proc/1/map_files/55a23af39000-55a23b05b000'
/lib/systemd/systemd

broken
# readlink '/proc/1/map_files/               55a23af39000-55a23b05b000'
/lib/systemd/systemd

broken
# readlink '/proc/1/map_files/55a23af39000-55a23b05b000    '
/lib/systemd/systemd

very broken
# readlink '/proc/1/map_files/1000000000000000055a23af39000-55a23b05b000'
/lib/systemd/systemd

Andrei said:

: This patch breaks criu.  It was a bug in criu.  And this bug is on a minor
: path, which works when memfd_create() isn't available.  It is a reason why
: I ask to not backport this patch to stable kernels.
:
: In CRIU this bug can be triggered, only if this patch will be backported
: to a kernel which version is lower than v3.16.

Link: http://lkml.kernel.org/r/20171120212706.GA14325@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/proc/base.c