From: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Subject: ntfs: fix validity check for file name attribute

When checking the file name attribute, we want to ensure that it fits within the bounds of ATTR_RECORD. To do this, we should check that (attr record + file name offset + file name length) < (attr record + attr record length).

However, the original check did not include the file name offset in the calculation. This means that corrupted on-disk metadata might not caught by the incorrect file name check, and lead to an invalid memory access.

An example can be seen in the crash report of a memory corruption error found by Syzbot: https://syzkaller.appspot.com/bug?id=a1a1e379b225812688566745c3e2f7242bffc24...

Adding the file name offset to the validity check fixes this error and passes the Syzbot reproducer test.

Link: https://lkml.kernel.org/r/20210614050540.289494-1-desmondcheongzx@gmail.com Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Reported-by: syzbot+213ac8bb98f7f4420840@syzkaller.appspotmail.com Tested-by: syzbot+213ac8bb98f7f4420840@syzkaller.appspotmail.com Acked-by: Anton Altaparmakov anton@tuxera.com Cc: Shuah Khan skhan@linuxfoundation.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/ntfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ntfs/inode.c~ntfs-fix-validity-check-for-file-name-attribute +++ a/fs/ntfs/inode.c @@ -477,7 +477,7 @@ err_corrupt_attr: } file_name_attr = (FILE_NAME_ATTR*)((u8*)attr + le16_to_cpu(attr->data.resident.value_offset)); - p2 = (u8*)attr + le32_to_cpu(attr->data.resident.value_length); + p2 = (u8 *)file_name_attr + le32_to_cpu(attr->data.resident.value_length); if (p2 < (u8*)attr || p2 > p) goto err_corrupt_attr; /* This attribute is ok, but is it in the $Extend directory? */ _