[PATCH] ppc64: iommu vmerge fix

This fixes a bug in the PPC64 iommu vmerge code which results in the
potential for iommu_unmap_sg to go off unmapping more than it should.

This was found on a test system which resulted in PCI bus errors due to
PCI memory being unmapped while DMAs were still in progress.

Signed-off-by: Brian King <brking@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/ppc64/kernel/iommu.c b/arch/ppc64/kernel/iommu.c
index 8316426ccaf6..845eebd1e28d 100644
--- a/arch/ppc64/kernel/iommu.c
+++ b/arch/ppc64/kernel/iommu.c
@@ -242,7 +242,7 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
         dma_addr_t dma_next = 0, dma_addr;
         unsigned long flags;
         struct scatterlist *s, *outs, *segstart;
-        int outcount;
+        int outcount, incount;
         unsigned long handle;
 
         BUG_ON(direction == DMA_NONE);
@@ -252,6 +252,7 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 
         outs = s = segstart = &sglist[0];
         outcount = 1;
+        incount = nelems;
         handle = 0;
 
         /* Init first segment length for backout at failure */
@@ -338,10 +339,10 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 
         DBG("mapped %d elements:\n", outcount);
 
-        /* For the sake of iommu_free_sg, we clear out the length in the
+        /* For the sake of iommu_unmap_sg, we clear out the length in the
          * next entry of the sglist if we didn't fill the list completely
          */
-        if (outcount < nelems) {
+        if (outcount < incount) {
                 outs++;
                 outs->dma_address = DMA_ERROR_CODE;
                 outs->dma_length = 0;