diff options
authorRoman Gushchin <klamm@yandex-team.ru>2015-02-11 15:28:39 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-03-18 13:22:27 +0100
commit992f1caea7af5c94e56bb7de089848470e1c000a (patch)
parent1a25fb791ab61358715554597701d7d708be9c63 (diff)
mm/mmap.c: fix arithmetic overflow in __vm_enough_memory()
commit 5703b087dc8eaf47bfb399d6cf512d471beff405 upstream. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 43a7089c6a7c..70ff9b41c970 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -127,7 +127,7 @@ 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;
@@ -193,7 +193,7 @@ 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)