ovl: use the pinned upper dir in ovl_fix_origin()

Renames made directly on the upper filesystem during a lookup crash the
kernel.

A dentry that is passed to vfs_setxattr() must be pinned.
ovl_fix_origin() passes upper->d_parent to ovl_set_impure() without a
reference, and the lookup holds no lock of the upper directory. A
rename on the upper filesystem changes d_parent, and only the child
pins the new parent, so a second rename and an rmdir free it.

With delays in ovl_fix_origin() and ovl_set_impure(), renaming the upper
directory twice and removing the intermediate parent during the lookup
of a merge directory without an origin xattr gave a KASAN
use-after-free in vfs_setxattr().

Fix this by passing the upper dentry that the overlay parent holds.

Fixes: 9678e6303057 ("ovl: fix inconsistent d_ino for legacy merge dir")
Cc: stable@vger.kernel.org
Signed-off-by: Chris Mason <mason@kernel.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[amir: add helper ovl_set_impure_dir()]
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

0 files changed, 0 insertions, 0 deletions