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NFSD: WARN when freeing an item still linked via nf_lru

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[ 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>
This commit is contained in:
Chuck Lever 2022-07-08 14:25:04 -04:00 • committed by Ksawlii
parent 2310e47e13
commit 2e3445246e
1 changed files with 10 additions and 2 deletions
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12
fs/nfsd/filecache.c
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@ -213,6 +213,14 @@ nfsd_file_free(struct nfsd_file *nf)
fput(nf->nf_file); fput(nf->nf_file);
flush = true; 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); call_rcu(&nf->nf_rcu, nfsd_file_slab_free);
return flush; return flush;
} }
@ -342,7 +350,7 @@ nfsd_file_dispose_list(struct list_head *dispose)
while(!list_empty(dispose)) { while(!list_empty(dispose)) {
nf = list_first_entry(dispose, struct nfsd_file, nf_lru); 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_flush(nf);
nfsd_file_put_noref(nf); nfsd_file_put_noref(nf);
} }
@ -356,7 +364,7 @@ nfsd_file_dispose_list_sync(struct list_head *dispose)
while(!list_empty(dispose)) { while(!list_empty(dispose)) {
nf = list_first_entry(dispose, struct nfsd_file, nf_lru); 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_flush(nf);
if (!refcount_dec_and_test(&nf->nf_ref)) if (!refcount_dec_and_test(&nf->nf_ref))
continue; continue;