Validate vertex and index buffer alignment (#7929)

Author: andyleiserson

cts_runner/test.lst

@@ -29,8 +29,8 @@ webgpu:api,validation,encoding,cmds,index_access:*
 //FAIL: webgpu:api,validation,encoding,cmds,render,draw:*
 webgpu:api,validation,encoding,cmds,render,draw:index_buffer_OOB:*
 webgpu:api,validation,encoding,cmds,render,draw:unused_buffer_bound:*
-webgpu:api,validation,encoding,cmds,render,setIndexBuffer:index_buffer_state:*
-webgpu:api,validation,encoding,cmds,render,setVertexBuffer:vertex_buffer_state:*
+webgpu:api,validation,encoding,cmds,render,setIndexBuffer:*
+webgpu:api,validation,encoding,cmds,render,setVertexBuffer:*
 webgpu:api,validation,encoding,encoder_state:*
 webgpu:api,validation,encoding,encoder_open_state:non_pass_commands:*
 webgpu:api,validation,encoding,encoder_open_state:render_pass_commands:*

wgpu-core/src/command/bundle.rs

@@ -622,6 +622,13 @@ fn set_index_buffer(
     buffer.same_device(&state.device)?;
     buffer.check_usage(wgt::BufferUsages::INDEX)?;
 
+    if offset % u64::try_from(index_format.byte_size()).unwrap() != 0 {
+        return Err(RenderCommandError::UnalignedIndexBuffer {
+            offset,
+            alignment: index_format.byte_size(),
+        }
+        .into());
+    }
     let end = offset + buffer.resolve_binding_size(offset, size)?;
 
     state
@@ -663,6 +670,9 @@ fn set_vertex_buffer(
     buffer.same_device(&state.device)?;
     buffer.check_usage(wgt::BufferUsages::VERTEX)?;
 
+    if offset % wgt::VERTEX_ALIGNMENT != 0 {
+        return Err(RenderCommandError::UnalignedVertexBuffer { slot, offset }.into());
+    }
     let end = offset + buffer.resolve_binding_size(offset, size)?;
 
     state

wgpu-core/src/command/draw.rs

@@ -73,6 +73,12 @@ pub enum RenderCommandError {
     BindGroupIndexOutOfRange(#[from] pass::BindGroupIndexOutOfRange),
     #[error("Vertex buffer index {index} is greater than the device's requested `max_vertex_buffers` limit {max}")]
     VertexBufferIndexOutOfRange { index: u32, max: u32 },
+    #[error(
+        "Offset {offset} for vertex buffer in slot {slot} is not a multiple of `VERTEX_ALIGNMENT`"
+    )]
+    UnalignedVertexBuffer { slot: u32, offset: u64 },
+    #[error("Offset {offset} for index buffer is not a multiple of {alignment}")]
+    UnalignedIndexBuffer { offset: u64, alignment: usize },
     #[error("Render pipeline targets are incompatible with render pass")]
     IncompatiblePipelineTargets(#[from] crate::device::RenderPassCompatibilityError),
     #[error("{0} writes to depth, while the pass has read-only depth access")]
@@ -116,6 +122,8 @@ impl WebGpuError for RenderCommandError {
 
             Self::BindGroupIndexOutOfRange { .. }
             | Self::VertexBufferIndexOutOfRange { .. }
+            | Self::UnalignedIndexBuffer { .. }
+            | Self::UnalignedVertexBuffer { .. }
             | Self::IncompatibleDepthAccess(..)
             | Self::IncompatibleStencilAccess(..)
             | Self::InvalidViewportRectSize { .. }

wgpu-core/src/command/render.rs

@@ -2344,6 +2344,13 @@ fn set_index_buffer(
 
     buffer.check_usage(BufferUsages::INDEX)?;
 
+    if offset % u64::try_from(index_format.byte_size()).unwrap() != 0 {
+        return Err(RenderCommandError::UnalignedIndexBuffer {
+            offset,
+            alignment: index_format.byte_size(),
+        }
+        .into());
+    }
     let (binding, resolved_size) = buffer
         .binding(offset, size, state.general.snatch_guard)
         .map_err(RenderCommandError::from)?;
@@ -2397,6 +2404,9 @@ fn set_vertex_buffer(
 
     buffer.check_usage(BufferUsages::VERTEX)?;
 
+    if offset % wgt::VERTEX_ALIGNMENT != 0 {
+        return Err(RenderCommandError::UnalignedVertexBuffer { slot, offset }.into());
+    }
     let (binding, buffer_size) = buffer
         .binding(offset, size, state.general.snatch_guard)
         .map_err(RenderCommandError::from)?;

wgpu-core/src/device/resource.rs

@@ -3159,7 +3159,7 @@ impl Device {
                     limit: self.limits.max_vertex_buffer_array_stride,
                 });
             }
-            if vb_state.array_stride % wgt::VERTEX_STRIDE_ALIGNMENT != 0 {
+            if vb_state.array_stride % wgt::VERTEX_ALIGNMENT != 0 {
                 return Err(pipeline::CreateRenderPipelineError::UnalignedVertexStride {
                     index: i as u32,
                     stride: vb_state.array_stride,

wgpu-core/src/pipeline.rs

@@ -512,7 +512,7 @@ pub enum CreateRenderPipelineError {
         given: u32,
         limit: u32,
     },
-    #[error("Vertex buffer {index} stride {stride} does not respect `VERTEX_STRIDE_ALIGNMENT`")]
+    #[error("Vertex buffer {index} stride {stride} does not respect `VERTEX_ALIGNMENT`")]
     UnalignedVertexStride {
         index: u32,
         stride: wgt::BufferAddress,

wgpu-types/src/lib.rs

@@ -97,10 +97,18 @@ pub const COPY_BUFFER_ALIGNMENT: BufferAddress = 4;
 /// [`get_mapped_range()`]: ../wgpu/struct.Buffer.html#method.get_mapped_range
 pub const MAP_ALIGNMENT: BufferAddress = 8;
 
+/// [Vertex buffer offsets] and [strides] have to be a multiple of this number.
+///
+/// [Vertex buffer offsets]: ../wgpu/util/trait.RenderEncoder.html#tymethod.set_vertex_buffer
+/// [strides]: ../wgpu/struct.VertexBufferLayout.html#structfield.array_stride
+pub const VERTEX_ALIGNMENT: BufferAddress = 4;
+
 /// [Vertex buffer strides] have to be a multiple of this number.
 ///
 /// [Vertex buffer strides]: ../wgpu/struct.VertexBufferLayout.html#structfield.array_stride
+#[deprecated(note = "Use `VERTEX_ALIGNMENT` instead", since = "27.0.0")]
 pub const VERTEX_STRIDE_ALIGNMENT: BufferAddress = 4;
+
 /// Ranges of [writes to push constant storage] must be at least this aligned.
 ///
 /// [writes to push constant storage]: ../wgpu/struct.RenderPass.html#method.set_push_constants

wgpu/src/api/render_pipeline.rs

@@ -76,7 +76,7 @@ impl RenderPipeline {
 pub struct VertexBufferLayout<'a> {
     /// The stride, in bytes, between elements of this buffer (between vertices).
     ///
-    /// This must be a multiple of [`VERTEX_STRIDE_ALIGNMENT`].
+    /// This must be a multiple of [`VERTEX_ALIGNMENT`].
     pub array_stride: BufferAddress,
     /// How often this vertex buffer is "stepped" forward.
     pub step_mode: VertexStepMode,

wgpu/src/lib.rs

@@ -90,8 +90,12 @@ pub use wgt::{
     TextureTransition, TextureUsages, TextureUses, TextureViewDimension, Trace, VertexAttribute,
     VertexFormat, VertexStepMode, WasmNotSend, WasmNotSendSync, WasmNotSync, COPY_BUFFER_ALIGNMENT,
     COPY_BYTES_PER_ROW_ALIGNMENT, MAP_ALIGNMENT, PUSH_CONSTANT_ALIGNMENT,
-    QUERY_RESOLVE_BUFFER_ALIGNMENT, QUERY_SET_MAX_QUERIES, QUERY_SIZE, VERTEX_STRIDE_ALIGNMENT,
+    QUERY_RESOLVE_BUFFER_ALIGNMENT, QUERY_SET_MAX_QUERIES, QUERY_SIZE, VERTEX_ALIGNMENT,
 };
+
+#[expect(deprecated)]
+pub use wgt::VERTEX_STRIDE_ALIGNMENT;
+
 // wasm-only types, we try to keep as many types non-platform
 // specific, but these need to depend on web-sys.
 #[cfg(web)]