ntfs: check for valid standard information attribute

commit 4dfe6bd94959222e18d512bdf15f6bf9edb9c27c upstream.

Mounting a corrupted filesystem with NTFS resulted in a kernel crash.

We should check for valid STANDARD_INFORMATION attribute offset and length
before trying to access it

Link: https://lkml.kernel.org/r/20210217155930.1506815-1-rkovhaev@gmail.com
Link: https://syzkaller.appspot.com/bug?extid=c584225dabdea2f71969
Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Reported-by: syzbot+c584225dabdea2f71969@syzkaller.appspotmail.com
Tested-by: syzbot+c584225dabdea2f71969@syzkaller.appspotmail.com
Acked-by: Anton Altaparmakov <anton@tuxera.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index caf5639..e9d5c8e 100644 (file)
--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -629,6 +629,12 @@ static int ntfs_read_locked_inode(struct inode *vi)
        }
        a = ctx->attr;
        /* Get the standard information attribute value. */
+       if ((u8 *)a + le16_to_cpu(a->data.resident.value_offset)
+                       + le32_to_cpu(a->data.resident.value_length) >
+                       (u8 *)ctx->mrec + vol->mft_record_size) {
+               ntfs_error(vi->i_sb, "Corrupt standard information attribute in inode.");
+               goto unm_err_out;
+       }
        si = (STANDARD_INFORMATION*)((u8*)a +
                        le16_to_cpu(a->data.resident.value_offset));