linux-kernel - [PATCH] [23/98] mmc: sdhci: Check mrq != NULL in sdhci_tasklet

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Message-Id: <20110727003515.6092B2403FF@tassilo.jf.intel.com>
Date:	Tue, 26 Jul 2011 17:35:15 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	cjb@...top.org, gregkh@...e.de, ak@...ux.intel.com,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	tim.bird@...sony.com, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH] [23/98] mmc: sdhci: Check mrq != NULL in sdhci_tasklet_finish

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Chris Ball <cjb@...top.org>

commit 0c9c99a765321104cc5f9c97f949382a9ba4927e upstream.

It seems that under certain circumstances the sdhci_tasklet_finish()
call can be entered with mrq set to NULL, causing the system to crash
with a NULL pointer de-reference.

Seen on S3C6410 system.  Based on a patch by Dimitris Papastamos.

Reported-by: Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
Signed-off-by: Chris Ball <cjb@...top.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 drivers/mmc/host/sdhci.c |    7 +++++++
 1 file changed, 7 insertions(+)

Index: linux-2.6.35.y/drivers/mmc/host/sdhci.c
===================================================================
--- linux-2.6.35.y.orig/drivers/mmc/host/sdhci.c
+++ linux-2.6.35.y/drivers/mmc/host/sdhci.c
@@ -1278,6 +1278,13 @@ static void sdhci_tasklet_finish(unsigne
 
 	host = (struct sdhci_host*)param;
 
+        /*
+         * If this tasklet gets rescheduled while running, it will
+         * be run again afterwards but without any active request.
+         */
+	if (!host->mrq)
+		return;
+
 	spin_lock_irqsave(&host->lock, flags);
 
 	del_timer(&host->timer);
--
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