Commit 672e4268 authored by Chen Zhongjin's avatar Chen Zhongjin Committed by Miklos Szeredi
Browse files

ovl: fix use inode directly in rcu-walk mode 



ovl_dentry_revalidate_common() can be called in rcu-walk mode.  As document
said, "in rcu-walk mode, d_parent and d_inode should not be used without
care".

Check inode here to protect access under rcu-walk mode.

Fixes: bccece1e ("ovl: allow remote upper")
Reported-and-tested-by: default avatar <syzbot+a4055c78774bbf3498bb@syzkaller.appspotmail.com>
Signed-off-by: default avatarChen Zhongjin <chenzhongjin@huawei.com>
Cc: <stable@vger.kernel.org> # v5.7
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent eb708140

fs/overlayfs/super.c

+6 −1
Original line number Diff line number Diff line
@@ -139,11 +139,16 @@ static int ovl_dentry_revalidate_common(struct dentry *dentry, 
					unsigned int flags, bool weak)

{

	struct ovl_entry *oe = dentry->d_fsdata;

	struct inode *inode = d_inode_rcu(dentry);

	struct dentry *upper;

	unsigned int i;

	int ret = 1;



	upper = ovl_dentry_upper(dentry);

	/* Careful in RCU mode */

	if (!inode)

		return -ECHILD;



	upper = ovl_i_dentry_upper(inode);

	if (upper)

		ret = ovl_revalidate_real(upper, flags, weak);