linux-kernel - [PATCH] nilfs2: fix a uaf in nilfs_find

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Message-ID: <tencent_4A46BB45335A9E721B634B011B242548BA08@qq.com>
Date: Tue, 12 Nov 2024 18:55:58 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+96d5d14c47d97015c624@...kaller.appspotmail.com
Cc: konishi.ryusuke@...il.com,
	linux-kernel@...r.kernel.org,
	linux-nilfs@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH] nilfs2: fix a uaf in nilfs_find_entry

The i_size value of the directory "cgroup.controllers" opened by openat is 0,
which causes 0 to be returned when calculating the last valid byte in
nilfs_last_byte(), which ultimately causes kaddr to move forward by reclen
(its value is 32 in this case), which ultimately triggers the uaf when
accessing de->rec_len in nilfs_find_entry().

To avoid this issue, add a check for i_size in nilfs_lookup().

Reported-by: syzbot+96d5d14c47d97015c624@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=96d5d14c47d97015c624
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 fs/nilfs2/namei.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/nilfs2/namei.c b/fs/nilfs2/namei.c
index 9b108052d9f7..0b57bcd9c2c5 100644
--- a/fs/nilfs2/namei.c
+++ b/fs/nilfs2/namei.c
@@ -60,6 +60,9 @@ nilfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 	if (dentry->d_name.len > NILFS_NAME_LEN)
 		return ERR_PTR(-ENAMETOOLONG);
 
+	if (!dir->i_size)
+		return ERR_PTR(-EINVAL);
+
 	res = nilfs_inode_by_name(dir, &dentry->d_name, &ino);
 	if (res) {
 		if (res != -ENOENT)
-- 
2.43.0