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NFSD: Fix possible sleep during nfsd4_release_lockowner()

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nfsd4_release_lockowner() holds clp->cl_lock when it calls
check_for_locks(). However, check_for_locks() calls nfsd_file_get()
/ nfsd_file_put() to access the backing inode's flc_posix list, and
nfsd_file_put() can sleep if the inode was recently removed.

Let's instead rely on the stateowner's reference count to gate
whether the release is permitted. This should be a reliable
indication of locks-in-use since file lock operations and
->lm_get_owner take appropriate references, which are released
appropriately when file locks are removed.

Reported-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Chuck Lever 2022-05-21 19:06:13 -04:00
parent fd5e363eac
commit ce3c4ad7f4
1 changed files with 4 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

12
fs/nfsd/nfs4state.c
View file

@ -7557,16 +7557,12 @@ nfsd4_release_lockowner(struct svc_rqst *rqstp,
if (sop->so_is_open_owner || !same_owner_str(sop, owner))
continue;
/* see if there are still any locks associated with it */
lo = lockowner(sop);
list_for_each_entry(stp, &sop->so_stateids, st_perstateowner) {
if (check_for_locks(stp->st_stid.sc_file, lo)) {
status = nfserr_locks_held;
spin_unlock(&clp->cl_lock);
return status;
}
if (atomic_read(&sop->so_count) != 1) {
spin_unlock(&clp->cl_lock);
return nfserr_locks_held;
}
lo = lockowner(sop);
nfs4_get_stateowner(sop);
break;
}