[PATCH] ntfs: check for valid standard information attribute

[Rustam Kovhaev <rkovhaev@gmail.com>]

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

Reported-and-tested-by: syzbot+c584225dabdea2f71969@syzkaller.appspotmail.com
Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Acked-by: Anton Altaparmakov <anton@tuxera.com>
Link: https://syzkaller.appspot.com/bug?extid=c584225dabdea2f71969
---
 fs/ntfs/inode.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index f7e4cbc26eaf..be4ff9386ec0 100644
--- 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));
 
-- 
2.30.0