diff options
| author | Zheng Liang <zhengliang6@huawei.com> | 2021-09-24 09:16:27 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-10-27 09:32:40 +0200 |
| commit | a4f281ffc1d128d7ea693cbc3a796e56e919fd7c (patch) | |
| tree | 198a8bd32f5d20288f87a7809f054f5632d71212 | |
| parent | c4078a9c958d90b9a89c1a19309ea4904632dd4a (diff) | |
ovl: fix missing negative dentry check in ovl_rename()
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>
Signed-off-by: Masami Ichikawa(CIP) <masami.ichikawa@cybertrust.co.jp>
| -rw-r--r-- | fs/overlayfs/dir.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index eedacae889b9..80bf0ab52e81 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -824,9 +824,13 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old, } } else { new_create = true; - 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) |