Patch "xen-blkfront: use a right index when checking requests" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

xen-blkfront: use a right index when checking requests

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xen-blkfront-use-a-right-index-when-checking-requests.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Munehisa Kamata <[email protected]>
Date: Wed, 9 Aug 2017 15:31:40 -0700
Subject: xen-blkfront: use a right index when checking requests

From: Munehisa Kamata <[email protected]>

commit b15bd8cb37598afb2963f7eb9e2de468d2d60a2f upstream.

Since commit d05d7f40791c ("Merge branch 'for-4.8/core' of
git://git.kernel.dk/linux-block") and 3fc9d690936f ("Merge branch 'for-4.8/drivers' of git://git.kernel.dk/linux-block"), blkfront_resume() has been using an index for iterating ring_info to check request when iterating blk_shadow in an inner loop. This seems to have been accidentally introduced during the massive rewrite of the block layer macros in the commits.

This may cause crash like this:

[11798.057074] BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
[11798.058832] IP: [<ffffffff814411fa>] blkfront_resume+0x10a/0x610
....
[11798.061063] Call Trace:
[11798.061063]  [<ffffffff8139ce93>] xenbus_dev_resume+0x53/0x140
[11798.061063]  [<ffffffff8139ce40>] ? xenbus_dev_probe+0x150/0x150
[11798.061063]  [<ffffffff813f359e>] dpm_run_callback+0x3e/0x110
[11798.061063]  [<ffffffff813f3a08>] device_resume+0x88/0x190
[11798.061063]  [<ffffffff813f4cc0>] dpm_resume+0x100/0x2d0
[11798.061063]  [<ffffffff813f5221>] dpm_resume_end+0x11/0x20
[11798.061063]  [<ffffffff813950a8>] do_suspend+0xe8/0x1a0
[11798.061063]  [<ffffffff813954bd>] shutdown_handler+0xfd/0x130
[11798.061063]  [<ffffffff8139aba0>] ? split+0x110/0x110
[11798.061063]  [<ffffffff8139ac26>] xenwatch_thread+0x86/0x120
[11798.061063]  [<ffffffff810b4570>] ? prepare_to_wait_event+0x110/0x110
[11798.061063]  [<ffffffff8108fe57>] kthread+0xd7/0xf0
[11798.061063]  [<ffffffff811da811>] ? kfree+0x121/0x170
[11798.061063]  [<ffffffff8108fd80>] ? kthread_park+0x60/0x60
[11798.061063]  [<ffffffff810863b0>] ?  call_usermodehelper_exec_work+0xb0/0xb0
[11798.061063]  [<ffffffff810864ea>] ?  call_usermodehelper_exec_async+0x13a/0x140
[11798.061063]  [<ffffffff81534a45>] ret_from_fork+0x25/0x30

Use the right index in the inner loop.

---
 drivers/block/xen-blkfront.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -2112,9 +2112,9 @@ static int blkfront_resume(struct xenbus
 			/*
 			 * Get the bios in the request so we can re-queue them.
 			 */
-			if (req_op(shadow[i].request) == REQ_OP_FLUSH ||
-			    req_op(shadow[i].request) == REQ_OP_DISCARD ||
-			    req_op(shadow[i].request) == REQ_OP_SECURE_ERASE ||
+			if (req_op(shadow[j].request) == REQ_OP_FLUSH ||
+			    req_op(shadow[j].request) == REQ_OP_DISCARD ||
+			    req_op(shadow[j].request) == REQ_OP_SECURE_ERASE ||
 			    shadow[j].request->cmd_flags & REQ_FUA) {
 				/*
 				 * Flush operations don't contain bios, so

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/xen-blkfront-use-a-right-index-when-checking-requests.patch