Patch "lib/iommu-common.c: do not try to deref a null iommu->lazy_flush() pointer when n < pool->hint" has been added to the 4.2-stable tree

[<gregkh@linuxfoundation.org>]

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

    lib/iommu-common.c: do not try to deref a null iommu->lazy_flush() pointer when n < pool->hint

to the 4.2-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:
     lib-iommu-common.c-do-not-try-to-deref-a-null-iommu-lazy_flush-pointer-when-n-pool-hint.patch
and it can be found in the queue-4.2 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 d046b770c9fc36ccb19c27afdb8322220108cbc7 Mon Sep 17 00:00:00 2001
From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Date: Tue, 22 Sep 2015 14:59:20 -0700
Subject: lib/iommu-common.c: do not try to deref a null iommu->lazy_flush() pointer when n < pool->hint

From: Sowmini Varadhan <sowmini.varadhan@oracle.com>

commit d046b770c9fc36ccb19c27afdb8322220108cbc7 upstream.

The check for invoking iommu->lazy_flush() from iommu_tbl_range_alloc()
has to be refactored so that we only call ->lazy_flush() if it is
non-null.

I had a sparc kernel that was crashing when I was trying to process some
very large perf.data files- the crash happens when the scsi driver calls
into dma_4v_map_sg and thus the iommu_tbl_range_alloc().

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 lib/iommu-common.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/lib/iommu-common.c
+++ b/lib/iommu-common.c
@@ -21,8 +21,7 @@ static	DEFINE_PER_CPU(unsigned int, iomm
 
 static inline bool need_flush(struct iommu_map_table *iommu)
 {
-	return (iommu->lazy_flush != NULL &&
-		(iommu->flags & IOMMU_NEED_FLUSH) != 0);
+	return ((iommu->flags & IOMMU_NEED_FLUSH) != 0);
 }
 
 static inline void set_flush(struct iommu_map_table *iommu)
@@ -211,7 +210,8 @@ unsigned long iommu_tbl_range_alloc(stru
 			goto bail;
 		}
 	}
-	if (n < pool->hint || need_flush(iommu)) {
+	if (iommu->lazy_flush &&
+	    (n < pool->hint || need_flush(iommu))) {
 		clear_flush(iommu);
 		iommu->lazy_flush(iommu);
 	}


Patches currently in stable-queue which might be from sowmini.varadhan@oracle.com are

queue-4.2/lib-iommu-common.c-do-not-try-to-deref-a-null-iommu-lazy_flush-pointer-when-n-pool-hint.patch