virt: acrn: Annotate struct vm_memory_region_batch with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct vm_memory_region_batch.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Fei Li <fei1.li@intel.com>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230922175102.work.020-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/drivers/virt/acrn/acrn_drv.h b/drivers/virt/acrn/acrn_drv.h
index 5663c17ad37c7800ec4c9b6bb6285e36649355f0..fb8438094f6f7e50747c5aa9e092d5ac3cd92187 100644 (file)
--- a/drivers/virt/acrn/acrn_drv.h
+++ b/drivers/virt/acrn/acrn_drv.h
@@ -60,7 +60,7 @@ struct vm_memory_region_batch {
        u16                        reserved[3];
        u32                        regions_num;
        u64                        regions_gpa;
-       struct vm_memory_region_op regions_op[];
+       struct vm_memory_region_op regions_op[] __counted_by(regions_num);
 };
 
 /**

diff --git a/drivers/virt/acrn/mm.c b/drivers/virt/acrn/mm.c
index b4ad8d452e9a1aa57e0c5349cf974577c28eed84..fa5d9ca6be5706fbe77bd952327c905447fe504f 100644 (file)
--- a/drivers/virt/acrn/mm.c
+++ b/drivers/virt/acrn/mm.c
@@ -250,11 +250,11 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
                ret = -ENOMEM;
                goto unmap_kernel_map;
        }
+       regions_info->regions_num = nr_regions;
 
        /* Fill each vm_memory_region_op */
        vm_region = regions_info->regions_op;
        regions_info->vmid = vm->vmid;
-       regions_info->regions_num = nr_regions;
        regions_info->regions_gpa = virt_to_phys(vm_region);
        user_vm_pa = memmap->user_vm_pa;
        i = 0;