This is a note to let you know that I've just added the patch titled
drm/ttm: Fix possible stack overflow by recursive shrinker calls.
to the 3.16-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:
drm-ttm-fix-possible-stack-overflow-by-recursive-shrinker-calls.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 71336e011d1d2312bcbcaa8fcec7365024f3a95d Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Sun, 3 Aug 2014 20:02:03 +0900
Subject: drm/ttm: Fix possible stack overflow by recursive shrinker calls.
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
commit 71336e011d1d2312bcbcaa8fcec7365024f3a95d upstream.
While ttm_dma_pool_shrink_scan() tries to take mutex before doing GFP_KERNEL
allocation, ttm_pool_shrink_scan() does not do it. This can result in stack
overflow if kmalloc() in ttm_page_pool_free() triggered recursion due to
memory pressure.
shrink_slab()
=> ttm_pool_shrink_scan()
=> ttm_page_pool_free()
=> kmalloc(GFP_KERNEL)
=> shrink_slab()
=> ttm_pool_shrink_scan()
=> ttm_page_pool_free()
=> kmalloc(GFP_KERNEL)
Change ttm_pool_shrink_scan() to do like ttm_dma_pool_shrink_scan() does.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/ttm/ttm_page_alloc.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
@@ -391,14 +391,17 @@ out:
static unsigned long
ttm_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
{
- static atomic_t start_pool = ATOMIC_INIT(0);
+ static DEFINE_MUTEX(lock);
+ static unsigned start_pool;
unsigned i;
- unsigned pool_offset = atomic_add_return(1, &start_pool);
+ unsigned pool_offset;
struct ttm_page_pool *pool;
int shrink_pages = sc->nr_to_scan;
unsigned long freed = 0;
- pool_offset = pool_offset % NUM_POOLS;
+ if (!mutex_trylock(&lock))
+ return SHRINK_STOP;
+ pool_offset = ++start_pool % NUM_POOLS;
/* select start pool in round robin fashion */
for (i = 0; i < NUM_POOLS; ++i) {
unsigned nr_free = shrink_pages;
@@ -408,6 +411,7 @@ ttm_pool_shrink_scan(struct shrinker *sh
shrink_pages = ttm_page_pool_free(pool, nr_free);
freed += nr_free - shrink_pages;
}
+ mutex_unlock(&lock);
return freed;
}
Patches currently in stable-queue which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
queue-3.16/drm-ttm-fix-possible-stack-overflow-by-recursive-shrinker-calls.patch
queue-3.16/drm-ttm-fix-possible-division-by-0-in-ttm_dma_pool_shrink_scan.patch
queue-3.16/drm-ttm-choose-a-pool-to-shrink-correctly-in-ttm_dma_pool_shrink_scan.patch
queue-3.16/drm-ttm-use-mutex_trylock-to-avoid-deadlock-inside-shrinker-functions.patch
queue-3.16/drm-ttm-pass-gfp-flags-in-order-to-avoid-deadlock.patch
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