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 4.1-stable tree

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 4.1-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-4.1 subdirectory.

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

From: Sowmini Varadhan <[email protected]>
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 <[email protected]>

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().

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

@@ -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 [email protected] are

queue-4.1/lib-iommu-common.c-do-not-try-to-deref-a-null-iommu-lazy_flush-pointer-when-n-pool-hint.patch