[XFS] stop re-checking permissions in xfs_swapext

xfs_swapext should simplify check if we have a writeable file descriptor
instead of re-checking the permissions using xfs_iaccess. Add an
additional check to refuse O_APPEND file descriptors because swapext is
not an append-only write operation.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:30369a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

1 files changed, 11 insertions, 9 deletions

diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
index 5d3285952ff7..3f53fad356a3 100644
--- a/fs/xfs/xfs_dfrag.c
+++ b/fs/xfs/xfs_dfrag.c
@@ -74,12 +74,23 @@ xfs_swapext(
                 goto out_free_sxp;
         }
 
+        if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND)) {
+                error = XFS_ERROR(EBADF);
+                goto out_put_file;
+        }
+
         target_file = fget((int)sxp->sx_fdtmp);
         if (!target_file) {
                 error = XFS_ERROR(EINVAL);
                 goto out_put_file;
         }
 
+        if (!(target_file->f_mode & FMODE_WRITE) ||
+            (target_file->f_flags & O_APPEND)) {
+                error = XFS_ERROR(EBADF);
+                goto out_put_target_file;
+        }
+
         ip = XFS_I(file->f_path.dentry->d_inode);
         tip = XFS_I(target_file->f_path.dentry->d_inode);
 
@@ -154,15 +165,6 @@ xfs_swap_extents(
         xfs_lock_inodes(ips, 2, 0, lock_flags);
         locked = 1;
 
-        /* Check permissions */
-        error = xfs_iaccess(ip, S_IWUSR, NULL);
-        if (error)
-                goto error0;
-
-        error = xfs_iaccess(tip, S_IWUSR, NULL);
-        if (error)
-                goto error0;
-
         /* Verify that both files have the same format */
         if ((ip->i_d.di_mode & S_IFMT) != (tip->i_d.di_mode & S_IFMT)) {
                 error = XFS_ERROR(EINVAL);