lkml.org 
[lkml]   [2016]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.10 01/24] locks: fix unlock when fcntl_setlk races with a close
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jeff Layton <jeff.layton@primarydata.com>

    commit 7f3697e24dc3820b10f445a4a7d914fc356012d1 upstream.

    Dmitry reported that he was able to reproduce the WARN_ON_ONCE that
    fires in locks_free_lock_context when the flc_posix list isn't empty.

    The problem turns out to be that we're basically rebuilding the
    file_lock from scratch in fcntl_setlk when we discover that the setlk
    has raced with a close. If the l_whence field is SEEK_CUR or SEEK_END,
    then we may end up with fl_start and fl_end values that differ from
    when the lock was initially set, if the file position or length of the
    file has changed in the interim.

    Fix this by just reusing the same lock request structure, and simply
    override fl_type value with F_UNLCK as appropriate. That ensures that
    we really are unlocking the lock that was initially set.

    While we're there, make sure that we do pop a WARN_ON_ONCE if the
    removal ever fails. Also return -EBADF in this event, since that's
    what we would have returned if the close had happened earlier.

    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Fixes: c293621bbf67 (stale POSIX lock handling)
    Reported-by: Dmitry Vyukov <dvyukov@google.com>
    Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
    Acked-by: "J. Bruce Fields" <bfields@fieldses.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/locks.c | 51 ++++++++++++++++++++++++++++++---------------------
    1 file changed, 30 insertions(+), 21 deletions(-)

    --- a/fs/locks.c
    +++ b/fs/locks.c
    @@ -1852,7 +1852,6 @@ int fcntl_setlk(unsigned int fd, struct
    goto out;
    }

    -again:
    error = flock_to_posix_lock(filp, file_lock, &flock);
    if (error)
    goto out;
    @@ -1883,19 +1882,22 @@ again:
    * Attempt to detect a close/fcntl race and recover by
    * releasing the lock that was just acquired.
    */
    - /*
    - * we need that spin_lock here - it prevents reordering between
    - * update of inode->i_flock and check for it done in close().
    - * rcu_read_lock() wouldn't do.
    - */
    - spin_lock(&current->files->file_lock);
    - f = fcheck(fd);
    - spin_unlock(&current->files->file_lock);
    - if (!error && f != filp && flock.l_type != F_UNLCK) {
    - flock.l_type = F_UNLCK;
    - goto again;
    + if (!error && file_lock->fl_type != F_UNLCK) {
    + /*
    + * We need that spin_lock here - it prevents reordering between
    + * update of inode->i_flock and check for it done in
    + * close(). rcu_read_lock() wouldn't do.
    + */
    + spin_lock(&current->files->file_lock);
    + f = fcheck(fd);
    + spin_unlock(&current->files->file_lock);
    + if (f != filp) {
    + file_lock->fl_type = F_UNLCK;
    + error = do_lock_file_wait(filp, cmd, file_lock);
    + WARN_ON_ONCE(error);
    + error = -EBADF;
    + }
    }
    -
    out:
    locks_free_lock(file_lock);
    return error;
    @@ -1970,7 +1972,6 @@ int fcntl_setlk64(unsigned int fd, struc
    goto out;
    }

    -again:
    error = flock64_to_posix_lock(filp, file_lock, &flock);
    if (error)
    goto out;
    @@ -2001,14 +2002,22 @@ again:
    * Attempt to detect a close/fcntl race and recover by
    * releasing the lock that was just acquired.
    */
    - spin_lock(&current->files->file_lock);
    - f = fcheck(fd);
    - spin_unlock(&current->files->file_lock);
    - if (!error && f != filp && flock.l_type != F_UNLCK) {
    - flock.l_type = F_UNLCK;
    - goto again;
    + if (!error && file_lock->fl_type != F_UNLCK) {
    + /*
    + * We need that spin_lock here - it prevents reordering between
    + * update of inode->i_flock and check for it done in
    + * close(). rcu_read_lock() wouldn't do.
    + */
    + spin_lock(&current->files->file_lock);
    + f = fcheck(fd);
    + spin_unlock(&current->files->file_lock);
    + if (f != filp) {
    + file_lock->fl_type = F_UNLCK;
    + error = do_lock_file_wait(filp, cmd, file_lock);
    + WARN_ON_ONCE(error);
    + error = -EBADF;
    + }
    }
    -
    out:
    locks_free_lock(file_lock);
    return error;

    \
     
     \ /
      Last update: 2016-03-08 01:21    [W:2.646 / U:0.580 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site