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author | Roman Gushchin <klamm@yandex-team.ru> | 2015-02-11 23:28:39 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-12 01:06:07 (GMT) |
commit | 5703b087dc8eaf47bfb399d6cf512d471beff405 (patch) | |
tree | 7891389716c896942b77627c6ea3b8033db8d24e /net | |
parent | 57c2e36b6f4dd52e7e90f4c748a665b13fa228d2 (diff) | |
download | linux-5703b087dc8eaf47bfb399d6cf512d471beff405.tar.xz |
mm/mmap.c: fix arithmetic overflow in __vm_enough_memory()
I noticed, that "allowed" can easily overflow by falling below 0,
because (total_vm / 32) can be larger than "allowed". The problem
occurs in OVERCOMMIT_NONE mode.
In this case, a huge allocation can success and overcommit the system
(despite OVERCOMMIT_NONE mode). All subsequent allocations will fall
(system-wide), so system become unusable.
The problem was masked out by commit c9b1d0981fcc
("mm: limit growth of 3% hardcoded other user reserve"),
but it's easy to reproduce it on older kernels:
1) set overcommit_memory sysctl to 2
2) mmap() large file multiple times (with VM_SHARED flag)
3) try to malloc() large amount of memory
It also can be reproduced on newer kernels, but miss-configured
sysctl_user_reserve_kbytes is required.
Fix this issue by switching to signed arithmetic here.
[akpm@linux-foundation.org: use min_t]
Signed-off-by: Roman Gushchin <klamm@yandex-team.ru>
Cc: Andrew Shewmaker <agshew@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'net')
0 files changed, 0 insertions, 0 deletions