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nfsd: fix potential race in nfs4_find_file

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The WARN_ON_ONCE check is not terribly useful. It also seems possible
for nfs4_find_file to race with the destruction of an fi_deleg_file
while trying to take a reference to it.

Now that it's safe to pass nfs_get_file a NULL pointer, remove the WARN
and NULL pointer check. Take the fi_lock when fetching fi_deleg_file.

Cc: NeilBrown <neilb@suse.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Jeff Layton 2023-01-06 10:33:48 -05:00 committed by Chuck Lever
parent 70f62231cd
commit bd6aaf781d
1 changed files with 9 additions and 6 deletions
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15
fs/nfsd/nfs4state.c
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@ -6404,23 +6404,26 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
static struct nfsd_file *
nfs4_find_file(struct nfs4_stid *s, int flags)
{
struct nfsd_file *ret = NULL;
if (!s)
return NULL;
switch (s->sc_type) {
case NFS4_DELEG_STID:
if (WARN_ON_ONCE(!s->sc_file->fi_deleg_file))
return NULL;
return nfsd_file_get(s->sc_file->fi_deleg_file);
spin_lock(&s->sc_file->fi_lock);
ret = nfsd_file_get(s->sc_file->fi_deleg_file);
spin_unlock(&s->sc_file->fi_lock);
break;
case NFS4_OPEN_STID:
case NFS4_LOCK_STID:
if (flags & RD_STATE)
return find_readable_file(s->sc_file);
ret = find_readable_file(s->sc_file);
else
return find_writeable_file(s->sc_file);
ret = find_writeable_file(s->sc_file);
}
return NULL;
return ret;
}
static __be32