The hugepage test cases of iommufd_dirty_tracking have the 64MB and 128MB coverages. Both of them are smaller than the default hugepage size 512MB, when CONFIG_PAGE_SIZE_64KB=y. However, these test cases have a variant of using huge pages, which would mmap(MAP_HUGETLB) using these smaller sizes than the system hugepag size. This results in the kernel aligning up the smaller size to 512MB. If a memory was located between the upper 64/128MB size boundary and the hugepage 512MB boundary, it would get wiped out: https://lore.kernel.org/all/aEoUhPYIAizTLADq@nvidia.com/

Given that this aligning up behavior is well documented, we have no choice but to allocate a hugepage aligned size to avoid this unintended wipe out. Instead of relying on the kernel's internal force alignment, pass the same size to posix_memalign() and map().

Also, fix the FIXTURE_TEARDOWN() misusing munmap() to free the memory from posix_memalign(), as munmap() doesn't destroy the allocator meta data. So, call free() instead.

Fixes: a9af47e382a4 ("iommufd/selftest: Test IOMMU_HWPT_GET_DIRTY_BITMAP") Cc: stable@vger.kernel.org Suggested-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com --- tools/testing/selftests/iommu/iommufd.c | 30 +++++++++++++++++-------- 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/iommu/iommufd.c b/tools/testing/selftests/iommu/iommufd.c index 1a8e85afe9aa..e7eb11a94034 100644 --- a/tools/testing/selftests/iommu/iommufd.c +++ b/tools/testing/selftests/iommu/iommufd.c @@ -2008,6 +2008,7 @@ FIXTURE_VARIANT(iommufd_dirty_tracking)

FIXTURE_SETUP(iommufd_dirty_tracking) { + size_t mmap_buffer_size; unsigned long size; int mmap_flags; void *vrc; @@ -2022,22 +2023,33 @@ FIXTURE_SETUP(iommufd_dirty_tracking) self->fd = open("/dev/iommu", O_RDWR); ASSERT_NE(-1, self->fd);

- rc = posix_memalign(&self->buffer, HUGEPAGE_SIZE, variant->buffer_size); - if (rc || !self->buffer) { - SKIP(return, "Skipping buffer_size=%lu due to errno=%d", - variant->buffer_size, rc); - } - mmap_flags = MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED; + mmap_buffer_size = variant->buffer_size; if (variant->hugepages) { /* * MAP_POPULATE will cause the kernel to fail mmap if THPs are * not available. */ mmap_flags |= MAP_HUGETLB | MAP_POPULATE; + + /* + * Allocation must be aligned to the HUGEPAGE_SIZE, because the + * following mmap() will automatically align the length to be a + * multiple of the underlying huge page size. Failing to do the + * same at this allocation will result in a memory overwrite by + * the mmap(). + */ + if (mmap_buffer_size < HUGEPAGE_SIZE) + mmap_buffer_size = HUGEPAGE_SIZE; + } + + rc = posix_memalign(&self->buffer, HUGEPAGE_SIZE, mmap_buffer_size); + if (rc || !self->buffer) { + SKIP(return, "Skipping buffer_size=%lu due to errno=%d", + mmap_buffer_size, rc); } assert((uintptr_t)self->buffer % HUGEPAGE_SIZE == 0); - vrc = mmap(self->buffer, variant->buffer_size, PROT_READ | PROT_WRITE, + vrc = mmap(self->buffer, mmap_buffer_size, PROT_READ | PROT_WRITE, mmap_flags, -1, 0); assert(vrc == self->buffer);

@@ -2066,8 +2078,8 @@ FIXTURE_SETUP(iommufd_dirty_tracking)

FIXTURE_TEARDOWN(iommufd_dirty_tracking) { - munmap(self->buffer, variant->buffer_size); - munmap(self->bitmap, DIV_ROUND_UP(self->bitmap_size, BITS_PER_BYTE)); + free(self->buffer); + free(self->bitmap); teardown_iommufd(self->fd, _metadata); }

The mfd and mfd_buffer will be used in the tests directly without an extra check. Test them in setup_sizes() to ensure they are safe to use.

Fixes: 0bcceb1f51c7 ("iommufd: Selftest coverage for IOMMU_IOAS_MAP_FILE") Cc: stable@vger.kernel.org Reviewed-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com --- tools/testing/selftests/iommu/iommufd.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/iommu/iommufd.c b/tools/testing/selftests/iommu/iommufd.c index e7eb11a94034..e61218c0537f 100644 --- a/tools/testing/selftests/iommu/iommufd.c +++ b/tools/testing/selftests/iommu/iommufd.c @@ -54,6 +54,8 @@ static __attribute__((constructor)) void setup_sizes(void)

mfd_buffer = memfd_mmap(BUFFER_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, &mfd); + assert(mfd_buffer != MAP_FAILED); + assert(mfd > 0); }

FIXTURE(iommufd)