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staging: zcache: fix crash on cpu remove

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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.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Seth Jennings 2011-10-06 14:28:26 -05:00 committed by Greg Kroah-Hartman
parent 5ba321cf17
commit 8550be08cb
1 changed files with 8 additions and 2 deletions
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10
drivers/staging/zcache/zcache-main.c
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@ -1357,8 +1357,14 @@ static int zcache_cpu_notifier(struct notifier_block *nb,
kp->objnodes[kp->nr - 1] = NULL;
kp->nr--;
}
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;
}
break;
default:
break;