From: Nicolin Chen nicoleotsuka@gmail.com
[ Upstream commit d5f583bf8654c231b781096bc1a186065cda72b3 ]
This is used to protect potential race condition at use_count. since probes of client drivers, calling attach_dev(), may run concurrently.
Signed-off-by: Nicolin Chen nicoleotsuka@gmail.com Tested-by: Dmitry Osipenko digetx@gmail.com Reviewed-by: Dmitry Osipenko digetx@gmail.com Acked-by: Thierry Reding treding@nvidia.com Link: https://lore.kernel.org/r/20201125101013.14953-3-nicoleotsuka@gmail.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/tegra-smmu.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c index fa0ecb5e63809..63679cce95054 100644 --- a/drivers/iommu/tegra-smmu.c +++ b/drivers/iommu/tegra-smmu.c @@ -252,26 +252,19 @@ static int tegra_smmu_alloc_asid(struct tegra_smmu *smmu, unsigned int *idp) { unsigned long id;
- mutex_lock(&smmu->lock); - id = find_first_zero_bit(smmu->asids, smmu->soc->num_asids); - if (id >= smmu->soc->num_asids) { - mutex_unlock(&smmu->lock); + if (id >= smmu->soc->num_asids) return -ENOSPC; - }
set_bit(id, smmu->asids); *idp = id;
- mutex_unlock(&smmu->lock); return 0; }
static void tegra_smmu_free_asid(struct tegra_smmu *smmu, unsigned int id) { - mutex_lock(&smmu->lock); clear_bit(id, smmu->asids); - mutex_unlock(&smmu->lock); }
static bool tegra_smmu_capable(enum iommu_cap cap) @@ -406,17 +399,21 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu, struct tegra_smmu_as *as) { u32 value; - int err; + int err = 0; + + mutex_lock(&smmu->lock);
if (as->use_count > 0) { as->use_count++; - return 0; + goto unlock; }
as->pd_dma = dma_map_page(smmu->dev, as->pd, 0, SMMU_SIZE_PD, DMA_TO_DEVICE); - if (dma_mapping_error(smmu->dev, as->pd_dma)) - return -ENOMEM; + if (dma_mapping_error(smmu->dev, as->pd_dma)) { + err = -ENOMEM; + goto unlock; + }
/* We can't handle 64-bit DMA addresses */ if (!smmu_dma_addr_valid(smmu, as->pd_dma)) { @@ -439,24 +436,35 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu, as->smmu = smmu; as->use_count++;
+ mutex_unlock(&smmu->lock); + return 0;
err_unmap: dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE); +unlock: + mutex_unlock(&smmu->lock); + return err; }
static void tegra_smmu_as_unprepare(struct tegra_smmu *smmu, struct tegra_smmu_as *as) { - if (--as->use_count > 0) + mutex_lock(&smmu->lock); + + if (--as->use_count > 0) { + mutex_unlock(&smmu->lock); return; + }
tegra_smmu_free_asid(smmu, as->id);
dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE);
as->smmu = NULL; + + mutex_unlock(&smmu->lock); }
static int tegra_smmu_attach_dev(struct iommu_domain *domain,