xen-blkfront: fix kernel panic with negotiate_mq error path

mbpatil369 · jgross1 · commit 6cc4a0863c97 · 2018-11-06T10:33:36.000+01:00
info->nr_rings isn't adjusted in case of ENOMEM error from negotiate_mq(). This leads to kernel panic in error path. Typical call stack involving panic - torvalds#8 page_fault at ffffffff8175936f [exception RIP: blkif_free_ring+33] RIP: ffffffffa0149491 RSP: ffff8804f7673c08 RFLAGS: 00010292 ... torvalds#9 blkif_free at ffffffffa0149aaa [xen_blkfront] torvalds#10 talk_to_blkback at ffffffffa014c8cd [xen_blkfront] torvalds#11 blkback_changed at ffffffffa014ea8b [xen_blkfront] torvalds#12 xenbus_otherend_changed at ffffffff81424670 torvalds#13 backend_changed at ffffffff81426dc3 torvalds#14 xenwatch_thread at ffffffff81422f29 torvalds#15 kthread at ffffffff810abe6a torvalds#16 ret_from_fork at ffffffff81754078 Cc: stable@vger.kernel.org Fixes: 7ed8ce1 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs") Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com> Acked-by: Roger Pau Monné <roger.pau@citrix.com> Signed-off-by: Juergen Gross <jgross@suse.com>
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
@@ -1919,6 +1919,7 @@ static int negotiate_mq(struct blkfront_info *info)
 			      GFP_KERNEL);
 	if (!info->rinfo) {
 		xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info structure");
+		info->nr_rings = 0;
 		return -ENOMEM;
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -1919,6 +1919,7 @@ static int negotiate_mq(struct blkfront_info *info)`
`1919`	`1919`	`GFP_KERNEL);`
`1920`	`1920`	`if (!info->rinfo) {`
`1921`	`1921`	`xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info structure");`
	`1922`	`+ info->nr_rings = 0;`
`1922`	`1923`	`return -ENOMEM;`
`1923`	`1924`	`}`
`1924`	`1925`