__arm_lpae_unmap() returns size_t but was returning -ENOENT (negative error code) when encountering an unmapped PTE. Since size_t is unsigned, -ENOENT (typically -2) becomes a huge positive value (0xFFFFFFFFFFFFFFFE on 64-bit systems).
This corrupted value propagates through the call chain: __arm_lpae_unmap() returns -ENOENT as size_t -> arm_lpae_unmap_pages() returns it -> __iommu_unmap() adds it to iova address -> iommu_pgsize() triggers BUG_ON due to corrupted iova
This can cause IOVA address overflow in __iommu_unmap() loop and trigger BUG_ON in iommu_pgsize() from invalid address alignment.
Fix by returning 0 instead of -ENOENT. The WARN_ON already signals the error condition, and returning 0 (meaning "nothing unmapped") is the correct semantic for size_t return type. This matches the behavior of other io-pgtable implementations (io-pgtable-arm-v7s, io-pgtable-dart) which return 0 on error conditions.
Fixes: 3318f7b5cefb ("iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()") Cc: stable@vger.kernel.org Signed-off-by: Chaitanya Kulkarni ckulkarnilinux@gmail.com --- drivers/iommu/io-pgtable-arm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c index e6626004b323..05d63fe92e43 100644 --- a/drivers/iommu/io-pgtable-arm.c +++ b/drivers/iommu/io-pgtable-arm.c @@ -637,7 +637,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, pte = READ_ONCE(*ptep); if (!pte) { WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN)); - return -ENOENT; + return 0; }
/* If the size matches this level, we're in the right place */
On Fri, Dec 19, 2025 at 3:29 PM Chaitanya Kulkarni ckulkarnilinux@gmail.com wrote:
__arm_lpae_unmap() returns size_t but was returning -ENOENT (negative error code) when encountering an unmapped PTE. Since size_t is unsigned, -ENOENT (typically -2) becomes a huge positive value (0xFFFFFFFFFFFFFFFE on 64-bit systems).
This corrupted value propagates through the call chain: __arm_lpae_unmap() returns -ENOENT as size_t -> arm_lpae_unmap_pages() returns it -> __iommu_unmap() adds it to iova address -> iommu_pgsize() triggers BUG_ON due to corrupted iova
This can cause IOVA address overflow in __iommu_unmap() loop and trigger BUG_ON in iommu_pgsize() from invalid address alignment.
Fix by returning 0 instead of -ENOENT. The WARN_ON already signals the error condition, and returning 0 (meaning "nothing unmapped") is the correct semantic for size_t return type. This matches the behavior of other io-pgtable implementations (io-pgtable-arm-v7s, io-pgtable-dart) which return 0 on error conditions.
Fixes: 3318f7b5cefb ("iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()") Cc: stable@vger.kernel.org Signed-off-by: Chaitanya Kulkarni ckulkarnilinux@gmail.com
Reviewed-by: Rob Clark robin.clark@oss.qualcomm.com
drivers/iommu/io-pgtable-arm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c index e6626004b323..05d63fe92e43 100644 --- a/drivers/iommu/io-pgtable-arm.c +++ b/drivers/iommu/io-pgtable-arm.c @@ -637,7 +637,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, pte = READ_ONCE(*ptep); if (!pte) { WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN));
return -ENOENT;
return 0; } /* If the size matches this level, we're in the right place */-- 2.40.0
On Fri, Dec 19, 2025 at 03:28:58PM -0800, Chaitanya Kulkarni wrote:
__arm_lpae_unmap() returns size_t but was returning -ENOENT (negative error code) when encountering an unmapped PTE. Since size_t is unsigned, -ENOENT (typically -2) becomes a huge positive value (0xFFFFFFFFFFFFFFFE on 64-bit systems).
This corrupted value propagates through the call chain: __arm_lpae_unmap() returns -ENOENT as size_t -> arm_lpae_unmap_pages() returns it -> __iommu_unmap() adds it to iova address -> iommu_pgsize() triggers BUG_ON due to corrupted iova
This can cause IOVA address overflow in __iommu_unmap() loop and trigger BUG_ON in iommu_pgsize() from invalid address alignment.
Fix by returning 0 instead of -ENOENT. The WARN_ON already signals the error condition, and returning 0 (meaning "nothing unmapped") is the correct semantic for size_t return type. This matches the behavior of other io-pgtable implementations (io-pgtable-arm-v7s, io-pgtable-dart) which return 0 on error conditions.
Fixes: 3318f7b5cefb ("iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()") Cc: stable@vger.kernel.org Signed-off-by: Chaitanya Kulkarni ckulkarnilinux@gmail.com
drivers/iommu/io-pgtable-arm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Jason Gunthorpe jgg@nvidia.com
At least the iommu_pgsize() path runs with !IO_PGTABLE_QUIRK_NO_WARN and we don't hit that WARN_ON() before the return, but the GPU folks using this NO_WARN path might have an issue so it should be fixed..
Jason
On Fri, Dec 19, 2025 at 03:28:58PM -0800, Chaitanya Kulkarni wrote:
__arm_lpae_unmap() returns size_t but was returning -ENOENT (negative error code) when encountering an unmapped PTE. Since size_t is unsigned, -ENOENT (typically -2) becomes a huge positive value (0xFFFFFFFFFFFFFFFE on 64-bit systems).
This corrupted value propagates through the call chain: __arm_lpae_unmap() returns -ENOENT as size_t -> arm_lpae_unmap_pages() returns it -> __iommu_unmap() adds it to iova address -> iommu_pgsize() triggers BUG_ON due to corrupted iova
This can cause IOVA address overflow in __iommu_unmap() loop and trigger BUG_ON in iommu_pgsize() from invalid address alignment.
Fix by returning 0 instead of -ENOENT. The WARN_ON already signals the error condition, and returning 0 (meaning "nothing unmapped") is the correct semantic for size_t return type. This matches the behavior of other io-pgtable implementations (io-pgtable-arm-v7s, io-pgtable-dart) which return 0 on error conditions.
Fixes: 3318f7b5cefb ("iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()") Cc: stable@vger.kernel.org Signed-off-by: Chaitanya Kulkarni ckulkarnilinux@gmail.com
drivers/iommu/io-pgtable-arm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c index e6626004b323..05d63fe92e43 100644 --- a/drivers/iommu/io-pgtable-arm.c +++ b/drivers/iommu/io-pgtable-arm.c @@ -637,7 +637,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, pte = READ_ONCE(*ptep); if (!pte) { WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN));
return -ENOENT;
return 0;/* If the size matches this level, we're in the right place */
Acked-by: Will Deacon will@kernel.org
Joerg -- please can you pick this one up for 6.19-rc?
Cheers,
Will
linux-stable-mirror@lists.linaro.org
-
Chaitanya Kulkarni -
Jason Gunthorpe -
Rob Clark -
Will Deacon