From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Date: Fri, 18 Sep 2015 11:49:50 +0000 (+0530)
Subject: lib/iommu-common.c: do not try to deref a null iommu->lazy_flush() pointer when n... 
X-Git-Tag: v4.1.12-92~270^2~1
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=4d16d5529b8e0e7afff8d5e6f1753c23d4e1fd30;p=users%2Fjedix%2Flinux-maple.git

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

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>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 02fa305981f7e2934173604f22789918cdaa6e3b)
(cherry picked from commit ca2de477dfdcfa0a1f32f95a701e81467438d3f4)
Signed-off-by: Allen Pais <allen.pais@oracle.com>
---

diff --git a/lib/iommu-common.c b/lib/iommu-common.c
index ff19f66d3f7f..b1c93e94ca7a 100644
--- a/lib/iommu-common.c
+++ b/lib/iommu-common.c
@@ -21,8 +21,7 @@ static	DEFINE_PER_CPU(unsigned int, iommu_hash_common);
 
 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(struct device *dev,
 			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);
 	}