iommu/iova: Don't BUG on invalid PFNs

[ Upstream commit d3e3d2be688b4b5864538de61e750721a311e4fc ]

Unlike the other instances which represent a complete loss of
consistency within the rcache mechanism itself, or a fundamental
and obvious misconfiguration by an IOMMU driver, the BUG_ON() in
iova_magazine_free_pfns() can be provoked at more or less any time
in a "spooky action-at-a-distance" manner by any old device driver
passing nonsense to dma_unmap_*() which then propagates through to
queue_iova().

Not only is this well outside the IOVA layer's control, it's also
nowhere near fatal enough to justify panicking anyway - all that
really achieves is to make debugging the offending driver more
difficult. Let's simply WARN and otherwise ignore bogus PFNs.

Reported-by: Prakash Gupta <guptap@codeaurora.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Prakash Gupta <guptap@codeaurora.org>
Link: https://lore.kernel.org/r/acbd2d092b42738a03a21b417ce64e27f8c91c86.1591103298.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index f106fd9..99c36a5 100644 (file)
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -676,7 +676,9 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
        for (i = 0 ; i < mag->size; ++i) {
                struct iova *iova = private_find_iova(iovad, mag->pfns[i]);
 
-               BUG_ON(!iova);
+               if (WARN_ON(!iova))
+                       continue;
+
                private_free_iova(iovad, iova);
        }