3.13.11-ckt18 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Roman Gushchin <klamm@xxxxxxxxxxxxxx> commit 8138a67a5557ffea3a21dfd6f037842d4e748513 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. Signed-off-by: Roman Gushchin <klamm@xxxxxxxxxxxxxx> Cc: Andrew Shewmaker <agshew@xxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- mm/nommu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/nommu.c b/mm/nommu.c index fec093a..0f28834 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1896,7 +1896,7 @@ EXPORT_SYMBOL(unmap_mapping_range); */ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) { - unsigned long free, allowed, reserve; + long free, allowed, reserve; vm_acct_memory(pages); @@ -1960,7 +1960,7 @@ 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) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html