5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chuck Lever chuck.lever@oracle.com
[ Upstream commit 668ed92e651d3c25f9b6e8cb7ceca54d00daa96d ]
Add a guardrail to prevent freeing memory that is still on a list. This includes either a dispose list or the LRU list.
This is the sign of a bug, but this class of bugs can be detected so that they don't endanger system stability, especially while debugging.
Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfsd/filecache.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 60c51a4d8e0d7..d9b5f1e183976 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -213,6 +213,14 @@ nfsd_file_free(struct nfsd_file *nf) fput(nf->nf_file); flush = true; } + + /* + * If this item is still linked via nf_lru, that's a bug. + * WARN and leak it to preserve system stability. + */ + if (WARN_ON_ONCE(!list_empty(&nf->nf_lru))) + return flush; + call_rcu(&nf->nf_rcu, nfsd_file_slab_free); return flush; } @@ -342,7 +350,7 @@ nfsd_file_dispose_list(struct list_head *dispose)
while(!list_empty(dispose)) { nf = list_first_entry(dispose, struct nfsd_file, nf_lru); - list_del(&nf->nf_lru); + list_del_init(&nf->nf_lru); nfsd_file_flush(nf); nfsd_file_put_noref(nf); } @@ -356,7 +364,7 @@ nfsd_file_dispose_list_sync(struct list_head *dispose)
while(!list_empty(dispose)) { nf = list_first_entry(dispose, struct nfsd_file, nf_lru); - list_del(&nf->nf_lru); + list_del_init(&nf->nf_lru); nfsd_file_flush(nf); if (!refcount_dec_and_test(&nf->nf_ref)) continue;