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 c9b1d0981f
("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>
This commit is contained in:
parent
57c2e36b6f
commit
5703b087dc
@ -152,7 +152,7 @@ EXPORT_SYMBOL_GPL(vm_memory_committed);
|
||||
*/
|
||||
int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
|
||||
{
|
||||
unsigned long free, allowed, reserve;
|
||||
long free, allowed, reserve;
|
||||
|
||||
VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
|
||||
-(s64)vm_committed_as_batch * num_online_cpus(),
|
||||
@ -220,7 +220,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
|
||||
*/
|
||||
if (mm) {
|
||||
reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
|
||||
allowed -= min(mm->total_vm / 32, reserve);
|
||||
allowed -= min_t(long, mm->total_vm / 32, reserve);
|
||||
}
|
||||
|
||||
if (percpu_counter_read_positive(&vm_committed_as) < allowed)
|
||||
|
Loading…
Reference in New Issue
Block a user