[PATCH 5.4 05/17] ntfs: check for valid standard information attribute

[Greg Kroah-Hartman]

From: Rustam Kovhaev <rkovhaev@xxxxxxxxx>

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@xxxxxxxxx
Link: https://syzkaller.appspot.com/bug?extid=c584225dabdea2f71969
Signed-off-by: Rustam Kovhaev <rkovhaev@xxxxxxxxx>
Reported-by: syzbot+c584225dabdea2f71969@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+c584225dabdea2f71969@xxxxxxxxxxxxxxxxxxxxxxxxx
Acked-by: Anton Altaparmakov <anton@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/ntfs/inode.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -628,6 +628,12 @@ static int ntfs_read_locked_inode(struct
 	}
 	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));