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| author | Zheng Liang <zhengliang6@huawei.com> | 2021-09-24 09:16:27 +0800 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2021-09-24 21:00:31 +0200 |
| commit | a295aef603e109a47af355477326bd41151765b6 (patch) | |
| tree | 6c51213e683f2e13c04ec7ff7348695e86568fc4 /fs/overlayfs | |
| parent | 6880fa6c56601bb8ed59df6c30fd390cc5f6dd8f (diff) | |
| download | linux-a295aef603e109a47af355477326bd41151765b6.tar.bz2 | |
ovl: fix missing negative dentry check in ovl_rename()
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>
Diffstat (limited to 'fs/overlayfs')
| -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 1fefb2b8960e..93c7c267de93 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -1219,9 +1219,13 @@ static int ovl_rename(struct user_namespace *mnt_userns, struct inode *olddir, 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) |