iommu/iova: Make rcache limit_pfn handling more robust

When popping a pfn from an rcache, we are currently checking it directly
against limit_pfn for viability. Since this represents iova->pfn_lo, it
is technically possible for the corresponding iova->pfn_hi to be greater
than limit_pfn. Although we generally get away with it in practice since
limit_pfn is typically a power-of-two boundary and the IOVAs are
size-aligned, it's pretty trivial to make the iova_rcache_get() path
take the allocation size into account for complete safety.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index ca21196..15ff303 100644 (file)
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -406,7 +406,7 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
        unsigned long iova_pfn;
        struct iova *new_iova;
 
-       iova_pfn = iova_rcache_get(iovad, size, limit_pfn);
+       iova_pfn = iova_rcache_get(iovad, size, limit_pfn + 1);
        if (iova_pfn)
                return iova_pfn;
 
@@ -823,7 +823,7 @@ static unsigned long iova_magazine_pop(struct iova_magazine *mag,
 {
        BUG_ON(iova_magazine_empty(mag));
 
-       if (mag->pfns[mag->size - 1] >= limit_pfn)
+       if (mag->pfns[mag->size - 1] > limit_pfn)
                return 0;
 
        return mag->pfns[--mag->size];
@@ -977,7 +977,7 @@ static unsigned long iova_rcache_get(struct iova_domain *iovad,
        if (log_size >= IOVA_RANGE_CACHE_MAX_SIZE)
                return 0;
 
-       return __iova_rcache_get(&iovad->rcaches[log_size], limit_pfn);
+       return __iova_rcache_get(&iovad->rcaches[log_size], limit_pfn - size);
 }
 
 /*