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nfsd: fix use-after-free due to delegation race
commit548ec0805c
upstream. 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 suspectaba2072f45
"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> [Salvatore Bonaccorso: Backport for context changes to versions which do not have20b7d86f29
("nfsd: use boottime for lease expiry calculation")] Signed-off-by: Salvatore Bonaccorso <carnil@debian.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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parent
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commit
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1 changed files with 7 additions and 2 deletions
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@ -1041,6 +1041,11 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
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return 0;
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}
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static bool delegation_hashed(struct nfs4_delegation *dp)
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{
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return !(list_empty(&dp->dl_perfile));
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}
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static bool
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unhash_delegation_locked(struct nfs4_delegation *dp)
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{
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@ -1048,7 +1053,7 @@ unhash_delegation_locked(struct nfs4_delegation *dp)
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lockdep_assert_held(&state_lock);
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if (list_empty(&dp->dl_perfile))
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if (!delegation_hashed(dp))
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return false;
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dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID;
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@ -4406,7 +4411,7 @@ static void nfsd4_cb_recall_prepare(struct nfsd4_callback *cb)
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* queued for a lease break. Don't queue it again.
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*/
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spin_lock(&state_lock);
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if (dp->dl_time == 0) {
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if (delegation_hashed(dp) && dp->dl_time == 0) {
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dp->dl_time = get_seconds();
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list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru);
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}
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