From f63237f54cf18448728201a65e6c82018e807cd9 Mon Sep 17 00:00:00 2001 From: Daniel Mentz Date: Tue, 1 Oct 2024 18:53:57 -0700 Subject: [PATCH] iommu/arm-smmu-v3: Fix last_sid_idx calculation for sid_bits==32 The function arm_smmu_init_strtab_2lvl uses the expression ((1 << smmu->sid_bits) - 1) to calculate the largest StreamID value. However, this fails for the maximum allowed value of SMMU_IDR1.SIDSIZE which is 32. The C standard states: "If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined." With smmu->sid_bits being 32, the prerequisites for undefined behavior are met. We observed that the value of (1 << 32) is 1 and not 0 as we initially expected. Similar bit shift operations in arm_smmu_init_strtab_linear seem to not be affected, because it appears to be unlikely for an SMMU to have SMMU_IDR1.SIDSIZE set to 32 but then not support 2-level Stream tables This issue was found by Ryan Huang on our team. Fixes: ce410410f1a7 ("iommu/arm-smmu-v3: Add arm_smmu_strtab_l1/2_idx()") Signed-off-by: Daniel Mentz Link: https://lore.kernel.org/r/20241002015357.1766934-1-danielmentz@google.com Signed-off-by: Will Deacon --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c index 737c5b882355..b55327d6058e 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -3625,7 +3625,7 @@ static int arm_smmu_init_strtab_2lvl(struct arm_smmu_device *smmu) u32 l1size; struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg; unsigned int last_sid_idx = - arm_smmu_strtab_l1_idx((1 << smmu->sid_bits) - 1); + arm_smmu_strtab_l1_idx((1ULL << smmu->sid_bits) - 1); /* Calculate the L1 size, capped to the SIDSIZE. */ cfg->l2.num_l1_ents = min(last_sid_idx + 1, STRTAB_MAX_L1_ENTRIES);