[PATCH] staging: zcache: fix crash on cpu remove

From: Seth Jennings
Date: Thu Oct 06 2011 - 15:28:50 EST

In the case that a cpu is taken offline before zcache_do_preload() is
ever called on the cpu, the per-cpu zcache_preloads structure will
be uninitialized. In the CPU_DEAD case for zcache_cpu_notifier(),
kp->obj is not checked before calling kmem_cache_free() on it.
If it is NULL, a crash results.

This patch ensures that both kp->obj and kp->page are not NULL before
calling the respective free functions. In practice, just checking
one or the other should be sufficient since they are assigned together
in zcache_do_preload(), but I check both for safety.

Based on v3.1-rc8

Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
drivers/staging/zcache/zcache-main.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 462fbc2..41d1ba1 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1357,8 +1357,14 @@ static int zcache_cpu_notifier(struct notifier_block *nb,
kp->objnodes[kp->nr - 1] = NULL;
- kmem_cache_free(zcache_obj_cache, kp->obj);
- free_page((unsigned long)kp->page);
+ if (kp->obj) {
+ kmem_cache_free(zcache_obj_cache, kp->obj);
+ kp->obj = NULL;
+ }
+ if (kp->page) {
+ free_page((unsigned long)kp->page);
+ kp->page = NULL;
+ }

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