From: Jason Gunthorpe Date: Mon, 2 Mar 2026 22:22:52 +0000 (-0400) Subject: iommu: Do not call drivers for empty gathers X-Git-Tag: v7.0-rc7~29^2~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=90c5def10bea574b101b7a520c015ca81742183f;p=thirdparty%2Flinux.git iommu: Do not call drivers for empty gathers An empty gather is coded with start=U64_MAX, end=0 and several drivers go on to convert that to a size with: end - start + 1 Which gives 2 for an empty gather. This then causes Weird Stuff to happen (for example an UBSAN splat in VT-d) that is hopefully harmless, but maybe not. Prevent drivers from being called right in iommu_iotlb_sync(). Auditing shows that AMD, Intel, Mediatek and RSIC-V drivers all do things on these empty gathers. Further, there are several callers that can trigger empty gathers, especially in unusual conditions. For example iommu_map_nosync() will call a 0 size unmap on some error paths. Also in VFIO, iommupt and other places. Cc: stable@vger.kernel.org Reported-by: Janusz Krzysztofik Closes: https://lore.kernel.org/r/11145826.aFP6jjVeTY@jkrzyszt-mobl2.ger.corp.intel.com Signed-off-by: Jason Gunthorpe Reviewed-by: Lu Baolu Reviewed-by: Samiullah Khawaja Reviewed-by: Robin Murphy Reviewed-by: Vasant Hegde Signed-off-by: Joerg Roedel --- diff --git a/include/linux/iommu.h b/include/linux/iommu.h index 54b8b48c762e..555597b54083 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -980,7 +980,8 @@ static inline void iommu_flush_iotlb_all(struct iommu_domain *domain) static inline void iommu_iotlb_sync(struct iommu_domain *domain, struct iommu_iotlb_gather *iotlb_gather) { - if (domain->ops->iotlb_sync) + if (domain->ops->iotlb_sync && + likely(iotlb_gather->start < iotlb_gather->end)) domain->ops->iotlb_sync(domain, iotlb_gather); iommu_iotlb_gather_init(iotlb_gather);