[31/43] mmc: sdhci: Check mrq != NULL in sdhci_tasklet_finish

[Greg KH]

2.6.33-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Chris Ball <cjb@xxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Chris Ball <cjb@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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

--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1266,6 +1266,13 @@ 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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