| From a295aef603e109a47af355477326bd41151765b6 Mon Sep 17 00:00:00 2001 |
| From: Zheng Liang <zhengliang6@huawei.com> |
| Date: Fri, 24 Sep 2021 09:16:27 +0800 |
| Subject: ovl: fix missing negative dentry check in ovl_rename() |
| |
| From: Zheng Liang <zhengliang6@huawei.com> |
| |
| commit a295aef603e109a47af355477326bd41151765b6 upstream. |
| |
| The following reproducer |
| |
| mkdir lower upper work merge |
| touch lower/old |
| touch lower/new |
| mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge |
| rm merge/new |
| mv merge/old merge/new & unlink upper/new |
| |
| may result in this race: |
| |
| PROCESS A: |
| rename("merge/old", "merge/new"); |
| overwrite=true,ovl_lower_positive(old)=true, |
| ovl_dentry_is_whiteout(new)=true -> flags |= RENAME_EXCHANGE |
| |
| PROCESS B: |
| unlink("upper/new"); |
| |
| PROCESS A: |
| lookup newdentry in new_upperdir |
| call vfs_rename() with negative newdentry and RENAME_EXCHANGE |
| |
| Fix by adding the missing check for negative newdentry. |
| |
| Signed-off-by: Zheng Liang <zhengliang6@huawei.com> |
| Fixes: e9be9d5e76e3 ("overlay filesystem") |
| Cc: <stable@vger.kernel.org> # v3.18 |
| Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| fs/overlayfs/dir.c | 10 +++++++--- |
| 1 file changed, 7 insertions(+), 3 deletions(-) |
| |
| --- a/fs/overlayfs/dir.c |
| +++ b/fs/overlayfs/dir.c |
| @@ -1166,9 +1166,13 @@ static int ovl_rename(struct inode *oldd |
| goto out_dput; |
| } |
| } else { |
| - if (!d_is_negative(newdentry) && |
| - (!new_opaque || !ovl_is_whiteout(newdentry))) |
| - goto out_dput; |
| + if (!d_is_negative(newdentry)) { |
| + if (!new_opaque || !ovl_is_whiteout(newdentry)) |
| + goto out_dput; |
| + } else { |
| + if (flags & RENAME_EXCHANGE) |
| + goto out_dput; |
| + } |
| } |
| |
| if (olddentry == trap) |
