From 1c65d50315dbe160ed483c68f0d044adb2630b47 Mon Sep 17 00:00:00 2001 From: Chen Zhongjin Date: Mon, 28 Nov 2022 11:33:05 +0100 Subject: [PATCH] ovl: fix use inode directly in rcu-walk mode commit 672e4268b2863d7e4978dfed29552b31c2f9bd4e upstream. 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: bccece1ead36 ("ovl: allow remote upper") Reported-and-tested-by: syzbot+a4055c78774bbf3498bb@syzkaller.appspotmail.com Signed-off-by: Chen Zhongjin Cc: # v5.7 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/super.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index e2ed38c5f7210..b3675d13c1ac2 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -138,11 +138,16 @@ 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);