From 4132ba2ae2cf14c289e3fabc1c95ac244d643356 Mon Sep 17 00:00:00 2001 From: Samuel Moelius Date: Sun, 28 Jun 2026 15:23:32 +0000 Subject: [PATCH] iommufd/selftest: Avoid selftest dirty bitmap size wrap IOMMU_TEST_OP_DIRTY sizes its temporary dirty bitmap from length / page_size. Very large selftest ranges can make the DIV_ROUND_UP() additions wrap before allocation, producing a zero-length allocation while the later test_bit() loop still walks the original number of bits. The selftest helper does not need to support unbounded dirty bitmap sizes. Reject requests that would allocate more than SZ_16M for the temporary buffer. Fixes: 79ea4a496ab5 ("iommufd/selftest: Fix buffer read overrrun in the dirty test") Link: https://patch.msgid.link/r/20260628152331.82122.408afd7b466c.iommufd-test-dirty-bitmap-size-wrap@trailofbits.com Assisted-by: Codex:gpt-5.5-cyber-preview Signed-off-by: Samuel Moelius Signed-off-by: Jason Gunthorpe --- drivers/iommu/iommufd/selftest.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c index af07c642a526..7ee9441c25c3 100644 --- a/drivers/iommu/iommufd/selftest.c +++ b/drivers/iommu/iommufd/selftest.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -1695,6 +1696,9 @@ static int iommufd_test_dirty(struct iommufd_ucmd *ucmd, unsigned int mockpt_id, if (!page_size || !length || iova % page_size || length % page_size || !uptr) return -EINVAL; + max = length / page_size; + if (max > SZ_16M * BITS_PER_BYTE) + return -EOVERFLOW; hwpt = get_md_pagetable(ucmd, mockpt_id, &mock); if (IS_ERR(hwpt)) @@ -1705,7 +1709,6 @@ static int iommufd_test_dirty(struct iommufd_ucmd *ucmd, unsigned int mockpt_id, goto out_put; } - max = length / page_size; tmp = kvzalloc(DIV_ROUND_UP(max, BITS_PER_LONG) * sizeof(unsigned long), GFP_KERNEL_ACCOUNT); if (!tmp) {