lkml.org 
[lkml]   [2022]   [Jun]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.9 11/12] NFSD: Fix possible sleep during nfsd4_release_lockowner()
    Date
    From: Chuck Lever <chuck.lever@oracle.com>

    commit ce3c4ad7f4ce5db7b4f08a1e237d8dd94b39180b upstream.

    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
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/nfsd/nfs4state.c | 12 ++++--------
    1 file changed, 4 insertions(+), 8 deletions(-)

    --- a/fs/nfsd/nfs4state.c
    +++ b/fs/nfsd/nfs4state.c
    @@ -6342,16 +6342,12 @@ nfsd4_release_lockowner(struct svc_rqst
    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;
    }

    \
     
     \ /
      Last update: 2022-06-03 19:42    [W:6.012 / U:0.596 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site