From: Dongli Zhang <dongli.zhang@oracle.com>
Date: Wed, 23 Jan 2019 07:47:33 +0000 (+0800)
Subject: xen/blkback: do not BUG() for invalid blkif_request from frontend
X-Git-Tag: v4.1.12-124.31.3~305
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=5c82f4267ebdbf72fffbd94b403add2a7647677b;p=users%2Fjedix%2Flinux-maple.git

xen/blkback: do not BUG() for invalid blkif_request from frontend

Upstream commit 0e367ae46503 ("xen/blkback: correctly respond to unknown,
non-native requests") fixed a bug to correctly respond to unknown,
non-native requests,  e.g., BLKIF_OP_RESERVED_1 or BLKIF_OP_PACKET for
64-bit SLES 11 guests when using a 32-bit backend.

Although such fix is already in uek4, it is broken by commit f0af2f840606
("xen-blkback: move indirect req allocation out-of-line") that introduced
the BUG() again.

This patch removes the BUG() to avoid panic backend by invalid
blkif_request from frontend.

Orabug: 29199843

Fixes: f0af2f840606 ("xen-blkback: move indirect req allocation out-of-line")
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: Joe Jin <joe.jin@oracle.com>
Reviewed-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 28ecd79ba1572..34067af643d27 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -1254,26 +1254,28 @@ __do_block_io_op(struct xen_blkif_ring *ring)
 		 */
 		down_read(&ring->blkif->vbd_lock);
 
-		if (likely(valid_req)) {
-			switch (req.operation) {
-			case BLKIF_OP_READ:
-			case BLKIF_OP_WRITE:
-			case BLKIF_OP_WRITE_BARRIER:
-			case BLKIF_OP_FLUSH_DISKCACHE:
-			case BLKIF_OP_INDIRECT:
-				if (dispatch_rw_block_io(ring, &req, pending_req))
-					goto done;
-				break;
-			case BLKIF_OP_DISCARD:
-				if (dispatch_discard_io(ring, &req))
-					goto done;
-				break;
-			default:
-				BUG();
-			}
-		} else {
+		if (unlikely(!valid_req)) {
+			if (dispatch_other_io(ring, &req))
+				goto done;
+		}
+
+		switch (req.operation) {
+		case BLKIF_OP_READ:
+		case BLKIF_OP_WRITE:
+		case BLKIF_OP_WRITE_BARRIER:
+		case BLKIF_OP_FLUSH_DISKCACHE:
+		case BLKIF_OP_INDIRECT:
+			if (dispatch_rw_block_io(ring, &req, pending_req))
+				goto done;
+			break;
+		case BLKIF_OP_DISCARD:
+			if (dispatch_discard_io(ring, &req))
+				goto done;
+			break;
+		default:
 			if (dispatch_other_io(ring, &req))
 				goto done;
+			break;
 		}
 
 		/* Yield point for this unbounded loop. */