drm/i915: Use batch length instead of object size in command parser

Previously we couldn't trust the user-supplied batch length because
it came directly from userspace (i.e. untrusted code). It would have
affected what commands software parsed without regard to what hardware
would actually execute, leaving a potential hole.

With the parser now copying the user supplied batch buffer and writing
MI_NOP commands to any space after the copied region, we can safely use
the batch length input. This should be a performance win as the actual
batch length is frequently much smaller than the allocated object size.

v2: Fix handling of non-zero batch_start_offset

Issue: VIZ-4719
Signed-off-by: Brad Volkin <bradley.d.volkin@intel.com>
Reviewed-By: Jon Bloomfield <jon.bloomfield@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index 2a4ccac..a698b47 100644 (file)
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -850,11 +850,19 @@ finish:
 
 /* Returns a vmap'd pointer to dest_obj, which the caller must unmap */
 static u32 *copy_batch(struct drm_i915_gem_object *dest_obj,
-                      struct drm_i915_gem_object *src_obj)
+                      struct drm_i915_gem_object *src_obj,
+                      u32 batch_start_offset,
+                      u32 batch_len)
 {
        int ret = 0;
        int needs_clflush = 0;
-       u32 *src_addr, *dest_addr = NULL;
+       u32 *src_base, *dest_base = NULL;
+       u32 *src_addr, *dest_addr;
+       u32 offset = batch_start_offset / sizeof(*dest_addr);
+       u32 end = batch_start_offset + batch_len;
+
+       if (end > dest_obj->base.size || end > src_obj->base.size)
+               return ERR_PTR(-E2BIG);
 
        ret = i915_gem_obj_prepare_shmem_read(src_obj, &needs_clflush);
        if (ret) {
@@ -862,15 +870,17 @@ static u32 *copy_batch(struct drm_i915_gem_object *dest_obj,
                return ERR_PTR(ret);
        }
 
-       src_addr = vmap_batch(src_obj);
-       if (!src_addr) {
+       src_base = vmap_batch(src_obj);
+       if (!src_base) {
                DRM_DEBUG_DRIVER("CMD: Failed to vmap batch\n");
                ret = -ENOMEM;
                goto unpin_src;
        }
 
+       src_addr = src_base + offset;
+
        if (needs_clflush)
-               drm_clflush_virt_range((char *)src_addr, src_obj->base.size);
+               drm_clflush_virt_range((char *)src_addr, batch_len);
 
        ret = i915_gem_object_set_to_cpu_domain(dest_obj, true);
        if (ret) {
@@ -878,24 +888,27 @@ static u32 *copy_batch(struct drm_i915_gem_object *dest_obj,
                goto unmap_src;
        }
 
-       dest_addr = vmap_batch(dest_obj);
-       if (!dest_addr) {
+       dest_base = vmap_batch(dest_obj);
+       if (!dest_base) {
                DRM_DEBUG_DRIVER("CMD: Failed to vmap shadow batch\n");
                ret = -ENOMEM;
                goto unmap_src;
        }
 
-       memcpy(dest_addr, src_addr, src_obj->base.size);
-       if (dest_obj->base.size > src_obj->base.size)
-               memset((u8 *)dest_addr + src_obj->base.size, 0,
-                      dest_obj->base.size - src_obj->base.size);
+       dest_addr = dest_base + offset;
+
+       if (batch_start_offset != 0)
+               memset((u8 *)dest_base, 0, batch_start_offset);
+
+       memcpy(dest_addr, src_addr, batch_len);
+       memset((u8 *)dest_addr + batch_len, 0, dest_obj->base.size - end);
 
 unmap_src:
-       vunmap(src_addr);
+       vunmap(src_base);
 unpin_src:
        i915_gem_object_unpin_pages(src_obj);
 
-       return ret ? ERR_PTR(ret) : dest_addr;
+       return ret ? ERR_PTR(ret) : dest_base;
 }
 
 /**
@@ -1016,6 +1029,7 @@ static bool check_cmd(const struct intel_engine_cs *ring,
  * @batch_obj: the batch buffer in question
  * @shadow_batch_obj: copy of the batch buffer in question
  * @batch_start_offset: byte offset in the batch at which execution starts
+ * @batch_len: length of the commands in batch_obj
  * @is_master: is the submitting process the drm master?
  *
  * Parses the specified batch buffer looking for privilege violations as
@@ -1028,6 +1042,7 @@ int i915_parse_cmds(struct intel_engine_cs *ring,
                    struct drm_i915_gem_object *batch_obj,
                    struct drm_i915_gem_object *shadow_batch_obj,
                    u32 batch_start_offset,
+                   u32 batch_len,
                    bool is_master)
 {
        int ret = 0;
@@ -1035,7 +1050,8 @@ int i915_parse_cmds(struct intel_engine_cs *ring,
        struct drm_i915_cmd_descriptor default_desc = { 0 };
        bool oacontrol_set = false; /* OACONTROL tracking. See check_cmd() */
 
-       batch_base = copy_batch(shadow_batch_obj, batch_obj);
+       batch_base = copy_batch(shadow_batch_obj, batch_obj,
+                               batch_start_offset, batch_len);
        if (IS_ERR(batch_base)) {
                DRM_DEBUG_DRIVER("CMD: Failed to copy batch\n");
                return PTR_ERR(batch_base);
@@ -1044,11 +1060,11 @@ int i915_parse_cmds(struct intel_engine_cs *ring,
        cmd = batch_base + (batch_start_offset / sizeof(*cmd));
 
        /*
-        * We use the source object's size because the shadow object is as
+        * We use the batch length as size because the shadow object is as
         * large or larger and copy_batch() will write MI_NOPs to the extra
         * space. Parsing should be faster in some cases this way.
         */
-       batch_end = cmd + (batch_obj->base.size / sizeof(*batch_end));
+       batch_end = cmd + (batch_len / sizeof(*batch_end));
 
        while (cmd < batch_end) {
                const struct drm_i915_cmd_descriptor *desc;

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 25832e5..eb4d64f 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2965,6 +2965,7 @@ int i915_parse_cmds(struct intel_engine_cs *ring,
                    struct drm_i915_gem_object *batch_obj,
                    struct drm_i915_gem_object *shadow_batch_obj,
                    u32 batch_start_offset,
+                   u32 batch_len,
                    bool is_master);
 
 /* i915_suspend.c */

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index cadb04d..5973e20 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1421,6 +1421,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
                                      batch_obj,
                                      shadow_batch_obj,
                                      args->batch_start_offset,
+                                     args->batch_len,
                                      file->is_master);
                i915_gem_object_ggtt_unpin(shadow_batch_obj);