[PATCH v4] drm/v3d: bound CPU-job query writes to their destination BO

[Michael Bommarito <michael.bommarito@gmail.com>]

The V3D_SUBMIT_CPU CPU jobs take user-supplied offsets and indices and
consume them at exec time without checking that the accesses stay inside
their BO:

  - TIMESTAMP_QUERY and RESET_TIMESTAMP_QUERY write one u64 per query
    into bo[0] at a fully user-controlled per-query offset.
  - COPY_TIMESTAMP_QUERY copies one u64 per query into bo[0] at
    offset + i * stride, and reads each result from a user-controlled
    offset in the source bo[1].
  - COPY_PERFORMANCE_QUERY writes nperfmons * DRM_V3D_MAX_PERF_COUNTERS
    counter slots plus an availability slot into bo[0] at the same
    geometry.
  - INDIRECT_CSD reads three u32 work-group counts from bo[0] at a
    user-controlled offset, then writes each count back into the
    indirect BO at a user-controlled u32 index (wg_uniform_offsets[]).

A render-node user (DRM_RENDER_ALLOW, no master, no capability) can make
the handlers read or write past a BO's vmap mapping.

Validate the full access extent against the BO size once the BOs are
looked up, before the job is queued, rejecting out-of-range geometry
with -EINVAL. The copy extent offset + (count - 1) * stride + write_size
is computed in u64, mirroring the u8 * pointer arithmetic in the
executors: (count - 1) * stride is a u32 * u32 product that is exact in
u64, so one overflow check on the total guards the bound. The
performance slot count and the bare timestamp, copy-source and indirect
offsets are computed in u64 the same way, so a user value cannot wrap
the comparison.

Fixes: 18b8413b25b7 ("drm/v3d: Create a CPU job extension for a indirect CSD job")
Fixes: 9ba0ff3e083f ("drm/v3d: Create a CPU job extension for the timestamp query job")
Fixes: 34a101e64296 ("drm/v3d: Create a CPU job extension for the reset timestamp job")
Fixes: 6745f3e44a20 ("drm/v3d: Create a CPU job extension to copy timestamp query to a buffer")
Fixes: 209e8d2695ee ("drm/v3d: Create a CPU job extension for the copy performance query job")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
v4:
 - Rebase onto drm-misc-next (Maira Canal): this is a fix, but a
   reasonably large change and not a critical bug.
 - Reconcile with the "drm/v3d: Miscellaneous fixes" series [1]. Drop the
   INDIRECT_CSD NULL indirect-BO reject: [1] patch 2/3 ("drm/v3d: Reject
   invalid indirect BO handle in indirect CSD setup") already returns
   -ENOENT for a bad handle at parse time, so that check is redundant.
   This patch assumes that series lands first. The out-of-bounds
   offset/index checks here are still novel and unfixed by [1].
 - Declare the loop index i as u32 rather than int (Sashiko, Maira
   Canal): a signed index could go negative once count exceeds INT_MAX.
 - Trim the TIMESTAMP_QUERY comment and restore the v2 wording of the
   COPY_PERFORMANCE_QUERY comment (Maira Canal).
 - INDIRECT_CSD: name the rewrite target dst and the counts BO src, add
   the "3 == x, y, z workgroup dims" and 0xffffffff-sentinel comments,
   and rename the local to indirect_csd (Maira Canal).

[1] https://lore.kernel.org/dri-devel/20260703-v3d-cpu-job-fixes-v3-0-bc51b1f3eeb5@igalia.com/
v3: https://lore.kernel.org/all/20260617125811.3692951-1-michael.bommarito@gmail.com/
v2: https://lore.kernel.org/all/20260614211644.217116-1-michael.bommarito@gmail.com/
v1: https://lore.kernel.org/all/20260614131058.2525157-1-michael.bommarito@gmail.com/

 drivers/gpu/drm/v3d/v3d_submit.c | 126 +++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)

diff --git a/drivers/gpu/drm/v3d/v3d_submit.c b/drivers/gpu/drm/v3d/v3d_submit.c
index ee2ac2540ed50..277823b774bed 100644
--- a/drivers/gpu/drm/v3d/v3d_submit.c
+++ b/drivers/gpu/drm/v3d/v3d_submit.c
@@ -4,6 +4,8 @@
  * Copyright (C) 2023 Raspberry Pi
  */
 
+#include <linux/overflow.h>
+
 #include <drm/drm_print.h>
 #include <drm/drm_syncobj.h>
 
@@ -1300,6 +1302,126 @@ static const unsigned int cpu_job_bo_handle_count[] = {
 	[V3D_CPU_JOB_TYPE_COPY_PERFORMANCE_QUERY] = 1,
 };
 
+/* Reject offset + (count - 1) * stride + write_size if it leaves the BO. */
+static int
+v3d_check_copy_extent(struct drm_device *dev, size_t bo_size,
+		      u32 offset, u32 stride, u32 count, u64 write_size)
+{
+	u64 last;
+
+	if (!count)
+		return 0;
+
+	/*
+	 * The executors walk a u8 * cursor, so the furthest written byte is
+	 * offset + (count - 1) * stride + write_size, matching the pointer
+	 * arithmetic in v3d_copy_query_results()/v3d_copy_performance_query().
+	 * (count - 1) * stride is a u32 * u32 product that is exact in u64,
+	 * and offset + write_size stays far below the u64 range, so a single
+	 * overflow check guards the total.
+	 */
+	last = write_size + offset;
+	if (check_add_overflow((u64)(count - 1) * stride, last, &last) ||
+	    last > bo_size) {
+		drm_dbg(dev, "CPU job copy buffer exceeds the destination BO.\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Reject a query CPU job whose writes would land outside their BO. */
+static int
+v3d_cpu_job_bounds_check(struct v3d_cpu_job *job)
+{
+	struct drm_device *dev = &job->base.v3d->drm;
+	struct v3d_timestamp_query_info *tquery = &job->timestamp_query;
+	struct v3d_copy_query_results_info *copy = &job->copy;
+	u32 elem = copy->do_64bit ? sizeof(u64) : sizeof(u32);
+	struct v3d_bo *dst, *src;
+	u64 slots, write_size;
+	u32 i;
+
+	switch (job->job_type) {
+	case V3D_CPU_JOB_TYPE_TIMESTAMP_QUERY:
+	case V3D_CPU_JOB_TYPE_RESET_TIMESTAMP_QUERY:
+		/* Each query writes one u64 timestamp slot into bo[0]. */
+		dst = to_v3d_bo(job->base.bo[0]);
+
+		for (i = 0; i < tquery->count; i++) {
+			if ((u64)tquery->queries[i].offset + sizeof(u64) >
+			    dst->base.base.size)
+				goto err_range;
+		}
+		return 0;
+	case V3D_CPU_JOB_TYPE_COPY_TIMESTAMP_QUERY:
+		/* Copies one u64 per query from bo[1] into bo[0]. */
+		dst = to_v3d_bo(job->base.bo[0]);
+		src = to_v3d_bo(job->base.bo[1]);
+
+		for (i = 0; i < tquery->count; i++) {
+			if ((u64)tquery->queries[i].offset + sizeof(u64) >
+			    src->base.base.size)
+				goto err_range;
+		}
+
+		write_size = (copy->availability_bit ? 2 : 1) * elem;
+		return v3d_check_copy_extent(dev, dst->base.base.size,
+					     copy->offset, copy->stride,
+					     tquery->count, write_size);
+	case V3D_CPU_JOB_TYPE_COPY_PERFORMANCE_QUERY:
+		/*
+		 * Each query writes nperfmons * DRM_V3D_MAX_PERF_COUNTERS
+		 * counter slots into bo[0], plus an availability slot at
+		 * index ncounters. nperfmons and ncounters are user values,
+		 * so the slot count is computed overflow-safe.
+		 */
+		dst = to_v3d_bo(job->base.bo[0]);
+
+		slots = (u64)job->performance_query.nperfmons *
+			DRM_V3D_MAX_PERF_COUNTERS;
+		if (copy->availability_bit)
+			slots = max(slots,
+				    (u64)job->performance_query.ncounters + 1);
+
+		write_size = slots * elem;
+		return v3d_check_copy_extent(dev, dst->base.base.size,
+					     copy->offset, copy->stride,
+					     job->performance_query.count,
+					     write_size);
+	case V3D_CPU_JOB_TYPE_INDIRECT_CSD: {
+		struct v3d_indirect_csd_info *indirect_csd = &job->indirect_csd;
+
+		/* 3 is the three dimensions (x, y, z) of the workgroup counts. */
+		src = to_v3d_bo(job->base.bo[0]);
+		if ((u64)indirect_csd->offset + 3 * sizeof(u32) >
+		    src->base.base.size)
+			goto err_range;
+
+		dst = to_v3d_bo(indirect_csd->indirect);
+		for (i = 0; i < 3; i++) {
+			u32 uidx = indirect_csd->wg_uniform_offsets[i];
+
+			/*
+			 * 0xffffffff means "skip this rewrite", so the exec
+			 * path never writes that index and it needs no check.
+			 */
+			if (uidx != 0xffffffff &&
+			    (u64)uidx * sizeof(u32) + sizeof(u32) >
+			    dst->base.base.size)
+				goto err_range;
+		}
+		return 0;
+	}
+	default:
+		return 0;
+	}
+
+err_range:
+	drm_dbg(dev, "CPU job query offset exceeds the BO.\n");
+	return -EINVAL;
+}
+
 /**
  * v3d_submit_cpu_ioctl() - Submits a CPU job to the V3D.
  * @dev: DRM device
@@ -1364,6 +1486,10 @@ v3d_submit_cpu_ioctl(struct drm_device *dev, void *data,
 			goto fail;
 	}
 
+	ret = v3d_cpu_job_bounds_check(cpu_job);
+	if (ret)
+		goto fail;
+
 	if (cpu_job->job_type == V3D_CPU_JOB_TYPE_INDIRECT_CSD) {
 		ret = v3d_setup_csd_jobs_and_bos(&submit, &cpu_job->indirect_csd.args,
 						 NULL);

base-commit: 1acd235bc8b8cf62da1a2b497f3e8c5cf01a2205
-- 
2.53.0