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author | Seth Jennings <sjenning@linux.vnet.ibm.com> | 2012-08-29 21:58:45 (GMT) |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-09-05 19:06:48 (GMT) |
commit | 6d7d9798ad5c97ee4e911dd070dc12dc5ae55bd0 (patch) | |
tree | 3410ea845d1bbf31e33f839a39c720aa1e291d80 | |
parent | 6bd4a5d96c08dc2380f8053b1bd4f879f55cd3c9 (diff) | |
download | linux-fsl-qoriq-6d7d9798ad5c97ee4e911dd070dc12dc5ae55bd0.tar.xz |
staging: zcache: fix cleancache race condition with shrinker
This patch fixes a race condition that results in memory
corruption when using cleancache.
The race exists between the zcache shrinker handler,
shrink_zcache_memory() and cleancache_get_page().
In most cases, the shrinker will both evict a zbpg
from its buddy list and flush it from tmem before a
cleancache_get_page() occurs on that page. A subsequent
cleancache_get_page() will fail in the tmem layer.
In the rare case that two occur together and the
cleancache_get_page() path gets through the tmem
layer before the shrinker path can flush tmem,
zbud_decompress() does a check to see if the zbpg is a
"zombie", i.e. not on a buddy list, which means the shrinker
is in the process of reclaiming it. If the zbpg is a zombie,
zbud_decompress() returns -EINVAL.
However, this return code is being ignored by the caller,
zcache_pampd_get_data_and_free(), which results in the
caller of cleancache_get_page() thinking that the page has
been properly retrieved when it has not.
This patch modifies zcache_pampd_get_data_and_free() to
convey the failure up the stack so that the caller of
cleancache_get_page() knows the page retrieval failed.
This needs to be applied to stable trees as well.
zcache-main.c was named zcache.c before v3.1, so
I'm not sure how you want to handle trees earlier
than that.
Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | drivers/staging/zcache/zcache-main.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c index c214977..52b43b7 100644 --- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -1251,13 +1251,12 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *bufsize, bool raw, void *pampd, struct tmem_pool *pool, struct tmem_oid *oid, uint32_t index) { - int ret = 0; - BUG_ON(!is_ephemeral(pool)); - zbud_decompress((struct page *)(data), pampd); + if (zbud_decompress((struct page *)(data), pampd) < 0) + return -EINVAL; zbud_free_and_delist((struct zbud_hdr *)pampd); atomic_dec(&zcache_curr_eph_pampd_count); - return ret; + return 0; } /* |