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nfsd: Fix a soft lockup race in nfsd_file_mark_find_or_create()

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[ Upstream commit 90d2f1da832fd23290ef0c0d964d97501e5e8553 ]

If nfsd_file_mark_find_or_create() keeps winning the race for the
nfsd_file_fsnotify_group->mark_mutex against nfsd_file_mark_put()
then it can soft lock up, since fsnotify_add_inode_mark() ends
up always finding an existing entry.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Trond Myklebust 2020-01-06 13:20:47 -05:00 committed by Greg Kroah-Hartman
parent 4f726a2afb
commit fed639f7e1
1 changed files with 6 additions and 2 deletions
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8
fs/nfsd/filecache.c
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@ -133,9 +133,13 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf)
struct nfsd_file_mark,
nfm_mark));
mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex);
fsnotify_put_mark(mark);
if (likely(nfm))
if (nfm) {
fsnotify_put_mark(mark);
break;
}
/* Avoid soft lockup race with nfsd_file_mark_put() */
fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group);
fsnotify_put_mark(mark);
} else
mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex);