From fed639f7e1d5e562f58a1d2de87490e43831e519 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Mon, 6 Jan 2020 13:20:47 -0500 Subject: [PATCH] nfsd: Fix a soft lockup race in nfsd_file_mark_find_or_create() [ 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 Signed-off-by: J. Bruce Fields Signed-off-by: Sasha Levin --- fs/nfsd/filecache.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 3007b8945d38..51c08ae79063 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -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);