From: Zheng Liang <zhengliang6(a)huawei.com>
mainline inclusion
from mainline-v5.15-rc5
commit a295aef603e109a47af355477326bd41151765b6
category: bugfix
bugzilla: NA
CVE: NA
-------------------------------------------------
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(a)huawei.com>
Fixes: e9be9d5e76e3 ("overlay filesystem")
Cc: <stable(a)vger.kernel.org> # v3.18
Signed-off-by: Miklos Szeredi <mszeredi(a)redhat.com>
Reviewed-by: Zhang Yi <yi.zhang(a)huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang(a)huawei.com>
---
fs/overlayfs/dir.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 9902c1706be91..1de8ef95ad960 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -1188,9 +1188,13 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
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)
--
2.25.1