[PATCH 4.19 019/125] iommu/iova: Dont BUG on invalid PFNs

Greg Kroah-Hartman
2020-09-01T15:24:53Z

From: Robin Murphy <robin.murphy@arm.com>

[ 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>
---
drivers/iommu/iova.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 34c058c24b9d2..ce5cd05253db9 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -814,7 +814,9 @@ 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);
}

--
2.25.1