linux-kernel - [PATCH] nilfs2: reject invalid file types when reading inodes

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Message-ID: <20250710134952.29862-1-konishi.ryusuke@gmail.com>
Date: Thu, 10 Jul 2025 22:49:08 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-nilfs@...r.kernel.org,
	syzbot <syzbot+895c23f6917da440ed0d@...kaller.appspotmail.com>,
	syzkaller-bugs@...glegroups.com,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH] nilfs2: reject invalid file types when reading inodes

To prevent inodes with invalid file types from tripping through the
vfs and causing malfunctions or assertion failures, add a missing
sanity check when reading an inode from a block device.  If the file
type is not valid, treat it as a filesystem error.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@...il.com>
Reported-by: syzbot+895c23f6917da440ed0d@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=895c23f6917da440ed0d
Cc: stable@...r.kernel.org
Fixes: 05fe58fdc10d ("nilfs2: inode operations")
---
Hi Andrew, please apply this as a bug fix.

This fixes a missing check in nilfs2 that could allow invalid file
types to be imported from corrupted filesystem images, as reported by
syzbot following a recently added VFS assertion.

Thanks,
Ryusuke Konishi

 fs/nilfs2/inode.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 6613b8fcceb0..5cf7328d5360 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -472,11 +472,18 @@ static int __nilfs_read_inode(struct super_block *sb,
 		inode->i_op = &nilfs_symlink_inode_operations;
 		inode_nohighmem(inode);
 		inode->i_mapping->a_ops = &nilfs_aops;
-	} else {
+	} else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
+		   S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
 		inode->i_op = &nilfs_special_inode_operations;
 		init_special_inode(
 			inode, inode->i_mode,
 			huge_decode_dev(le64_to_cpu(raw_inode->i_device_code)));
+	} else {
+		nilfs_error(sb,
+			    "invalid file type bits in mode 0%o for inode %lu",
+			    inode->i_mode, ino);
+		err = -EIO;
+		goto failed_unmap;
 	}
 	nilfs_ifile_unmap_inode(raw_inode);
 	brelse(bh);
-- 
2.43.0