From: Linmao Li Date: Tue, 21 Jul 2026 01:15:58 +0000 (+0800) Subject: drm/vc4: Prevent shader BO mappings from becoming writable X-Git-Tag: v7.2-rc5~20^2~1^2~17 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0c9e6367639548307d3f578f6943ce72c9d39087;p=thirdparty%2Flinux.git drm/vc4: Prevent shader BO mappings from becoming writable vc4_gem_object_mmap() rejects a writable mapping of a validated shader BO, but leaves VM_MAYWRITE set. Userspace can map the BO read-only and then turn it writable with mprotect(). Validated shader BOs must stay read-only: the validator checks the instructions once and the GPU trusts them afterwards. A writable mapping lets userspace rewrite the code after validation, bypassing the validator. Clear VM_MAYWRITE on the read-only path so the mapping cannot be upgraded, as i915 already does for its read-only objects. Fixes: 463873d57014 ("drm/vc4: Add an API for creating GPU shaders in GEM BOs.") Cc: stable@vger.kernel.org Reported-by: Sashiko Closes: https://lore.kernel.org/dri-devel/20260720085554.B0AF01F000E9@smtp.kernel.org/ Signed-off-by: Linmao Li Link: https://patch.msgid.link/20260721011558.1672477-1-lilinmao@kylinos.cn Reviewed-by: Maíra Canal Signed-off-by: Maíra Canal --- diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c index 2161761b1f22..5e7c46dd7823 100644 --- a/drivers/gpu/drm/vc4/vc4_bo.c +++ b/drivers/gpu/drm/vc4/vc4_bo.c @@ -732,9 +732,13 @@ static int vc4_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struct { struct vc4_bo *bo = to_vc4_bo(obj); - if (bo->validated_shader && (vma->vm_flags & VM_WRITE)) { - DRM_DEBUG("mmapping of shader BOs for writing not allowed.\n"); - return -EINVAL; + if (bo->validated_shader) { + if (vma->vm_flags & VM_WRITE) { + DRM_DEBUG("mmapping of shader BOs for writing not allowed.\n"); + return -EINVAL; + } + + vm_flags_clear(vma, VM_MAYWRITE); } mutex_lock(&bo->madv_lock);