Patch "spi: fix race freeing dummy_tx/rx before it is unmapped" has been added to the 4.0-stable tree

[<gregkh@linuxfoundation.org>]

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

    spi: fix race freeing dummy_tx/rx before it is unmapped

to the 4.0-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:
     spi-fix-race-freeing-dummy_tx-rx-before-it-is-unmapped.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 8e76ef88f607174082023f50b87fe12dcdbe5db5 Mon Sep 17 00:00:00 2001
From: Martin Sperl <kernel@martin.sperl.org>
Date: Sun, 10 May 2015 07:50:45 +0000
Subject: spi: fix race freeing dummy_tx/rx before it is unmapped
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Martin Sperl <kernel@martin.sperl.org>

commit 8e76ef88f607174082023f50b87fe12dcdbe5db5 upstream.

Fix a race (with some kernel configurations) where a queued
master->pump_messages runs and frees dummy_tx/rx before
spi_unmap_msg is running (or is finished).

This results in the following messages:
  BUG: Bad page state in process
  page:db7ba030 count:0 mapcount:0 mapping:  (null) index:0x0
  flags: 0x200(arch_1)
  page dumped because: PAGE_FLAGS_CHECK_AT_PREP flag set
  ...

Reported-by: Noralf Trønnes <noralf@tronnes.org>
Suggested-by: Noralf Trønnes <noralf@tronnes.org>
Tested-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/spi/spi.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1091,9 +1091,6 @@ void spi_finalize_current_message(struct
 
 	spin_lock_irqsave(&master->queue_lock, flags);
 	mesg = master->cur_msg;
-	master->cur_msg = NULL;
-
-	queue_kthread_work(&master->kworker, &master->pump_messages);
 	spin_unlock_irqrestore(&master->queue_lock, flags);
 
 	spi_unmap_msg(master, mesg);
@@ -1106,9 +1103,13 @@ void spi_finalize_current_message(struct
 		}
 	}
 
-	trace_spi_message_done(mesg);
-
+	spin_lock_irqsave(&master->queue_lock, flags);
+	master->cur_msg = NULL;
 	master->cur_msg_prepared = false;
+	queue_kthread_work(&master->kworker, &master->pump_messages);
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+
+	trace_spi_message_done(mesg);
 
 	mesg->state = NULL;
 	if (mesg->complete)


Patches currently in stable-queue which might be from kernel@martin.sperl.org are

queue-4.0/spi-fix-race-freeing-dummy_tx-rx-before-it-is-unmapped.patch