From 3e977ac6179b39faa3c0eda5fce4f00663ae298d Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 12 Jul 2018 19:53:13 +0100 Subject: [PATCH] drm/i915: Prevent writing into a read-only object via a GGTT mmap If the user has created a read-only object, they should not be allowed to circumvent the write protection by using a GGTT mmapping. Deny it. Also most machines do not support read-only GGTT PTEs, so again we have to reject attempted writes. Fortunately, this is known a priori, so we can at least reject in the call to create the mmap (with a sanity check in the fault handler). v2: Check the vma->vm_flags during mmap() to allow readonly access. v3: Remove VM_MAYWRITE to curtail mprotect() Testcase: igt/gem_userptr_blits/readonly_mmap* Signed-off-by: Chris Wilson Cc: Jon Bloomfield Cc: Joonas Lahtinen Cc: Matthew Auld Cc: David Herrmann Reviewed-by: Matthew Auld #v1 Reviewed-by: Jon Bloomfield Reviewed-by: Joonas Lahtinen Link: https://patchwork.freedesktop.org/patch/msgid/20180712185315.3288-4-chris@chris-wilson.co.uk --- drivers/gpu/drm/drm_gem.c | 9 +++++++++ drivers/gpu/drm/i915/i915_gem.c | 4 ++++ drivers/gpu/drm/i915/i915_gem_gtt.c | 12 +++++++----- drivers/gpu/drm/i915/i915_gem_object.h | 13 ++++++++++++- drivers/gpu/drm/i915/intel_ringbuffer.c | 2 +- drivers/gpu/drm/i915/selftests/i915_gem_context.c | 5 +++-- include/drm/drm_vma_manager.h | 1 + 7 files changed, 37 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 4a16d7b26c89..bf90625df3c5 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -1036,6 +1036,15 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma) return -EACCES; } + if (node->readonly) { + if (vma->vm_flags & VM_WRITE) { + drm_gem_object_put_unlocked(obj); + return -EINVAL; + } + + vma->vm_flags &= ~VM_MAYWRITE; + } + ret = drm_gem_mmap_obj(obj, drm_vma_node_size(node) << PAGE_SHIFT, vma); diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index ed2be33ec58a..1910c66f48e2 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2012,6 +2012,10 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf) pgoff_t page_offset; int ret; + /* Sanity check that we allow writing into this object */ + if (i915_gem_object_is_readonly(obj) && write) + return VM_FAULT_SIGBUS; + /* We don't use vmf->pgoff since that has the fake offset */ page_offset = (vmf->address - area->vm_start) >> PAGE_SHIFT; diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index 86a9618bab24..3d75f2bb5623 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -206,7 +206,7 @@ static int ppgtt_bind_vma(struct i915_vma *vma, /* Applicable to VLV, and gen8+ */ pte_flags = 0; - if (vma->obj->gt_ro) + if (i915_gem_object_is_readonly(vma->obj)) pte_flags |= PTE_READ_ONLY; vma->vm->insert_entries(vma->vm, vma, cache_level, pte_flags); @@ -2491,8 +2491,10 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm, const gen8_pte_t pte_encode = gen8_pte_encode(0, level, 0); dma_addr_t addr; - /* The GTT does not support read-only mappings */ - GEM_BUG_ON(flags & PTE_READ_ONLY); + /* + * Note that we ignore PTE_READ_ONLY here. The caller must be careful + * not to allow the user to override access to a read only page. + */ gtt_entries = (gen8_pte_t __iomem *)ggtt->gsm; gtt_entries += vma->node.start >> PAGE_SHIFT; @@ -2731,7 +2733,7 @@ static int ggtt_bind_vma(struct i915_vma *vma, /* Applicable to VLV (gen8+ do not support RO in the GGTT) */ pte_flags = 0; - if (obj->gt_ro) + if (i915_gem_object_is_readonly(obj)) pte_flags |= PTE_READ_ONLY; intel_runtime_pm_get(i915); @@ -2769,7 +2771,7 @@ static int aliasing_gtt_bind_vma(struct i915_vma *vma, /* Currently applicable only to VLV */ pte_flags = 0; - if (vma->obj->gt_ro) + if (i915_gem_object_is_readonly(vma->obj)) pte_flags |= PTE_READ_ONLY; if (flags & I915_VMA_LOCAL_BIND) { diff --git a/drivers/gpu/drm/i915/i915_gem_object.h b/drivers/gpu/drm/i915/i915_gem_object.h index c3c6f2e588fb..56e9f00d2c4c 100644 --- a/drivers/gpu/drm/i915/i915_gem_object.h +++ b/drivers/gpu/drm/i915/i915_gem_object.h @@ -141,7 +141,6 @@ struct drm_i915_gem_object { * Is the object to be mapped as read-only to the GPU * Only honoured if hardware has relevant pte bit */ - unsigned long gt_ro:1; unsigned int cache_level:3; unsigned int cache_coherent:2; #define I915_BO_CACHE_COHERENT_FOR_READ BIT(0) @@ -358,6 +357,18 @@ static inline void i915_gem_object_unlock(struct drm_i915_gem_object *obj) reservation_object_unlock(obj->resv); } +static inline void +i915_gem_object_set_readonly(struct drm_i915_gem_object *obj) +{ + obj->base.vma_node.readonly = true; +} + +static inline bool +i915_gem_object_is_readonly(const struct drm_i915_gem_object *obj) +{ + return obj->base.vma_node.readonly; +} + static inline bool i915_gem_object_has_struct_page(const struct drm_i915_gem_object *obj) { diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 6de88add508a..69bd7f697f6d 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -1100,7 +1100,7 @@ intel_ring_create_vma(struct drm_i915_private *dev_priv, int size) * if supported by the platform's GGTT. */ if (vm->has_read_only) - obj->gt_ro = 1; + i915_gem_object_set_readonly(obj); vma = i915_vma_instance(obj, vm, NULL); if (IS_ERR(vma)) diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/selftests/i915_gem_context.c index 2e2a3c44b8e9..1c92560d35da 100644 --- a/drivers/gpu/drm/i915/selftests/i915_gem_context.c +++ b/drivers/gpu/drm/i915/selftests/i915_gem_context.c @@ -487,7 +487,8 @@ static int igt_ctx_readonly(void *arg) goto out_unlock; } - obj->gt_ro = prandom_u32_state(&prng); + if (prandom_u32_state(&prng) & 1) + i915_gem_object_set_readonly(obj); } intel_runtime_pm_get(i915); @@ -518,7 +519,7 @@ static int igt_ctx_readonly(void *arg) unsigned int num_writes; num_writes = rem; - if (obj->gt_ro) + if (i915_gem_object_is_readonly(obj)) num_writes = 0; err = cpu_check(obj, num_writes); diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h index 8758df94e9a0..c7987daeaed0 100644 --- a/include/drm/drm_vma_manager.h +++ b/include/drm/drm_vma_manager.h @@ -41,6 +41,7 @@ struct drm_vma_offset_node { rwlock_t vm_lock; struct drm_mm_node vm_node; struct rb_root vm_files; + bool readonly:1; }; struct drm_vma_offset_manager {