This is a note to let you know that I've just added the patch titled
mm/mmap.c: fix arithmetic overflow in __vm_enough_memory()
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-mmap.c-fix-arithmetic-overflow-in-__vm_enough_memory.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5703b087dc8eaf47bfb399d6cf512d471beff405 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <klamm@xxxxxxxxxxxxxx>
Date: Wed, 11 Feb 2015 15:28:39 -0800
Subject: mm/mmap.c: fix arithmetic overflow in __vm_enough_memory()
From: Roman Gushchin <klamm@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxx: use min_t]
Signed-off-by: Roman Gushchin <klamm@xxxxxxxxxxxxxx>
Cc: Andrew Shewmaker <agshew@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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
*/
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)
Patches currently in stable-queue which might be from klamm@xxxxxxxxxxxxxx are
queue-3.19/mm-mmap.c-fix-arithmetic-overflow-in-__vm_enough_memory.patch
queue-3.19/mm-nommu.c-fix-arithmetic-overflow-in-__vm_enough_memory.patch
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