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authorJ. Bruce Fields <bfields@citi.umich.edu>2008-02-20 14:02:47 -0500
committerJ. Bruce Fields <bfields@citi.umich.edu>2008-04-23 16:13:39 -0400
commit164f98adbbd50c67177b096a59f55c1a56a45c82 (patch)
treebaa47455b18219eca8ff4a54a84954170597fa06
parentdd35210e1e2cb46d6dba5c97f1bc3784c4f97998 (diff)
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lockd: fix race in nlm_release()
The sm_count is decremented to zero but left on the nsm_handles list. So in the space between decrementing sm_count and acquiring nsm_mutex, it is possible for another task to find this nsm_handle, increment the use count and then enter nsm_release itself. Thus there's nothing to prevent the nsm being freed before we acquire nsm_mutex here. Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
-rw-r--r--fs/lockd/host.c10
1 files changed, 4 insertions, 6 deletions
diff --git a/fs/lockd/host.c b/fs/lockd/host.c
index c3f119426d8..960911c4a11 100644
--- a/fs/lockd/host.c
+++ b/fs/lockd/host.c
@@ -529,12 +529,10 @@ nsm_release(struct nsm_handle *nsm)
{
if (!nsm)
return;
+ mutex_lock(&nsm_mutex);
if (atomic_dec_and_test(&nsm->sm_count)) {
- mutex_lock(&nsm_mutex);
- if (atomic_read(&nsm->sm_count) == 0) {
- list_del(&nsm->sm_link);
- kfree(nsm);
- }
- mutex_unlock(&nsm_mutex);
+ list_del(&nsm->sm_link);
+ kfree(nsm);
}
+ mutex_unlock(&nsm_mutex);
}