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authorJeff Layton <jeff.layton@primarydata.com>2016-01-07 16:38:10 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-03-09 15:31:53 -0800
commit29ec60ccee541893e18a749044084fc2caa79137 (patch)
tree582ef9ac73501c4744410cad3c62ccd0f8be6507
parente39c17904aadf3a107b2bc292c03bfd9f850fd08 (diff)
downloadlinux-linaro-stable-29ec60ccee541893e18a749044084fc2caa79137.tar.gz
locks: fix unlock when fcntl_setlk races with a close
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>
-rw-r--r--fs/locks.c51
1 files changed, 30 insertions, 21 deletions
diff --git a/fs/locks.c b/fs/locks.c
index 0274c953b07d..f7b1de7e6735 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1852,7 +1852,6 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
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, struct file *filp, unsigned int cmd,
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;