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.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
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 0cf2e44e874f..6bb37d3abbaa 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -221,6 +221,14 @@ 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;
}
@@ -350,7 +358,7 @@ 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);
}
@@ -364,7 +372,7 @@ 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;
