From: Jan Kara Date: Thu, 6 Feb 2025 09:44:55 +0000 (+0100) Subject: ext4: verify fast symlink length X-Git-Tag: v6.15-rc1~145^2~22 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5f920d5d60839f7cbbb1ed50eac68d8bc0a73a7c;p=thirdparty%2Fkernel%2Flinux.git ext4: verify fast symlink length Verify fast symlink length stored in inode->i_size matches the string stored in the inode to avoid surprises from corrupted filesystems. Reported-by: syzbot+48a99e426f29859818c0@syzkaller.appspotmail.com Tested-by: syzbot+48a99e426f29859818c0@syzkaller.appspotmail.com Fixes: bae80473f7b0 ("ext4: use inode_set_cached_link()") Suggested-by: Darrick J. Wong Signed-off-by: Jan Kara Reviewed-by: Baokun Li Reviewed-by: Darrick J. Wong Link: https://patch.msgid.link/20250206094454.20522-2-jack@suse.cz Signed-off-by: Theodore Ts'o --- diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index fc3e1b474e2c0..7d965338c7d20 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5029,8 +5029,16 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, inode->i_op = &ext4_encrypted_symlink_inode_operations; } else if (ext4_inode_is_fast_symlink(inode)) { inode->i_op = &ext4_fast_symlink_inode_operations; - nd_terminate_link(ei->i_data, inode->i_size, - sizeof(ei->i_data) - 1); + if (inode->i_size == 0 || + inode->i_size >= sizeof(ei->i_data) || + strnlen((char *)ei->i_data, inode->i_size + 1) != + inode->i_size) { + ext4_error_inode(inode, function, line, 0, + "invalid fast symlink length %llu", + (unsigned long long)inode->i_size); + ret = -EFSCORRUPTED; + goto bad_inode; + } inode_set_cached_link(inode, (char *)ei->i_data, inode->i_size); } else {