diff options
| author | J. Bruce Fields <bfields@redhat.com> | 2021-11-29 15:08:00 -0500 |
|---|---|---|
| committer | J. Bruce Fields <bfields@redhat.com> | 2021-12-10 11:55:15 -0500 |
| commit | 548ec0805c399c65ed66c6641be467f717833ab5 (patch) | |
| tree | f8c3f64767ecff4aa77f22157f38465a9e333f26 | |
| parent | b10252c7ae9c9d7c90552f88b544a44ee773af64 (diff) | |
nfsd: fix use-after-free due to delegation race
A delegation break could arrive as soon as we've called vfs_setlease. A
delegation break runs a callback which immediately (in
nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we
then exit nfs4_set_delegation without hashing the delegation, it will be
freed as soon as the callback is done with it, without ever being
removed from del_recall_lru.
Symptoms show up later as use-after-free or list corruption warnings,
usually in the laundromat thread.
I suspect aba2072f4523 "nfsd: grant read delegations to clients holding
writes" made this bug easier to hit, but I looked as far back as v3.0
and it looks to me it already had the same problem. So I'm not sure
where the bug was introduced; it may have been there from the beginning.
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
| -rw-r--r-- | fs/nfsd/nfs4state.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index bfad94c70b84..1956d377d1a6 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1207,6 +1207,11 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp) return 0; } +static bool delegation_hashed(struct nfs4_delegation *dp) +{ + return !(list_empty(&dp->dl_perfile)); +} + static bool unhash_delegation_locked(struct nfs4_delegation *dp) { @@ -1214,7 +1219,7 @@ unhash_delegation_locked(struct nfs4_delegation *dp) lockdep_assert_held(&state_lock); - if (list_empty(&dp->dl_perfile)) + if (!delegation_hashed(dp)) return false; dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID; @@ -4598,7 +4603,7 @@ static void nfsd4_cb_recall_prepare(struct nfsd4_callback *cb) * queued for a lease break. Don't queue it again. */ spin_lock(&state_lock); - if (dp->dl_time == 0) { + if (delegation_hashed(dp) && dp->dl_time == 0) { dp->dl_time = ktime_get_boottime_seconds(); list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru); } |