| Message ID | 20180614160648.28172-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> -----Original Message----- > From: Chris Wilson <chris@chris-wilson.co.uk> > Sent: Thursday, June 14, 2018 9:07 AM > To: intel-gfx@lists.freedesktop.org > Cc: dri-devel@lists.freedesktop.org; Chris Wilson <chris@chris-wilson.co.uk>; > Bloomfield, Jon <jon.bloomfield@intel.com>; Joonas Lahtinen > <joonas.lahtinen@linux.intel.com>; Matthew Auld > <matthew.william.auld@gmail.com>; David Herrmann > <dh.herrmann@gmail.com> > Subject: [PATCH v2] 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. > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Jon Bloomfield <jon.bloomfield@intel.com> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> > Cc: Matthew Auld <matthew.william.auld@gmail.com> > Cc: David Herrmann <dh.herrmann@gmail.com> Shame about the BUG_ON, but probably overkill to add code to suppress the RO flag just for mmap. Reviewed-by: Jon Bloomfield <jon.bloomfield@intel.com>
Quoting Bloomfield, Jon (2018-06-14 17:36:29) > > -----Original Message----- > > From: Chris Wilson <chris@chris-wilson.co.uk> > > Sent: Thursday, June 14, 2018 9:07 AM > > To: intel-gfx@lists.freedesktop.org > > Cc: dri-devel@lists.freedesktop.org; Chris Wilson <chris@chris-wilson.co.uk>; > > Bloomfield, Jon <jon.bloomfield@intel.com>; Joonas Lahtinen > > <joonas.lahtinen@linux.intel.com>; Matthew Auld > > <matthew.william.auld@gmail.com>; David Herrmann > > <dh.herrmann@gmail.com> > > Subject: [PATCH v2] 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. > > > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > > Cc: Jon Bloomfield <jon.bloomfield@intel.com> > > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> > > Cc: Matthew Auld <matthew.william.auld@gmail.com> > > Cc: David Herrmann <dh.herrmann@gmail.com> > > Shame about the BUG_ON, but probably overkill to add code to suppress > the RO flag just for mmap. > > Reviewed-by: Jon Bloomfield <jon.bloomfield@intel.com> Maybe one day with a PIN_RO, we can put it back in again. Just a feeling of unease for shadowing cache_level on the vma. If only we could just erase the history of doing cache_domain tracking. -Chris
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 4a16d7b26c89..230863813905 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -1036,6 +1036,11 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma) return -EACCES; } + if (vma->vm_flags & VM_WRITE && node->readonly) { + drm_gem_object_put_unlocked(obj); + return -EINVAL; + } + 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 8dd4d35655af..2bfb16e83af2 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2009,6 +2009,10 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf) unsigned int flags; 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 ca84616fbe24..d57f0154b6cc 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -198,7 +198,7 @@ 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); @@ -2416,8 +2416,10 @@ 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; @@ -2656,7 +2658,7 @@ 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); @@ -2694,7 +2696,7 @@ 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 54f00b350779..66e30aa4b7da 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) @@ -367,6 +366,12 @@ static inline void i915_gem_object_unlock(struct drm_i915_gem_object *obj) reservation_object_unlock(obj->resv); } +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 8853a5e6d421..d18033bc65df 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -1112,7 +1112,7 @@ 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; + obj->base.vma_node.readonly = true; 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 5bae52068926..c02c4940c013 100644 --- a/drivers/gpu/drm/i915/selftests/i915_gem_context.c +++ b/drivers/gpu/drm/i915/selftests/i915_gem_context.c @@ -510,7 +510,8 @@ static int igt_ctx_readonly(void *arg) goto out_unlock; } - obj->gt_ro = prandom_u32_state(&prng); + if (prandom_u32_state(&prng) & 1) + obj->base.vma_node.readonly = true; } intel_runtime_pm_get(i915); @@ -539,7 +540,7 @@ static int igt_ctx_readonly(void *arg) unsigned int rem = min_t(unsigned int, ndwords - dw, max_dwords(obj)); - if (obj->gt_ro) + if (i915_gem_object_is_readonly(obj)) err = ro_check(obj, rem); else err = cpu_check(obj, rem); 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 {
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. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Jon Bloomfield <jon.bloomfield@intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Matthew Auld <matthew.william.auld@gmail.com> Cc: David Herrmann <dh.herrmann@gmail.com> --- drivers/gpu/drm/drm_gem.c | 5 +++++ 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 | 7 ++++++- 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, 27 insertions(+), 9 deletions(-)