From 164f98adbbd50c67177b096a59f55c1a56a45c82 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Wed, 20 Feb 2008 14:02:47 -0500 Subject: [PATCH] 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 --- fs/lockd/host.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/fs/lockd/host.c b/fs/lockd/host.c index c3f119426d83..960911c4a11c 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); }