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| author | Zheng Liang <zhengliang6@huawei.com> | 2021-09-24 09:16:27 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@google.com> | 2021-10-24 13:58:34 +0200 |
| commit | a7378d1307f39b4765b8dfae6f35d48e453e350c (patch) | |
| tree | 7d9b7fce6d4f4ee538953a59833dda0ac7bdfb86 | |
| parent | ea69efd32cadfdc1bdb86f7bb84a0f23a1c0798f (diff) | |
| download | mediatek-a7378d1307f39b4765b8dfae6f35d48e453e350c.tar.gz | |
UPSTREAM: 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>
Change-Id: I7938aa3fe6c1ff00eaad1e85e945ee8686db2b4f
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
| -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 90a11f4542fb..65e5921f26df 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -855,9 +855,13 @@ 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) |