[PATCH 6.18.y] accel/amdxdna: Bound the sync_bo flush range to the BO size

[Eva Crystal <0xiviel@gmail.com>]

[ Upstream commit dbc8fd7a03cbc0704e8e558a448015f620547a02 ]

amdxdna_drm_sync_bo_ioctl() passes the caller's offset and size to
drm_clflush_virt_range() on the BO's kernel mapping without checking
either against the BO size. The ioctl has no permission flags: any
process that can open the accel node controls the offset. Any BO with a
kernel mapping reaches that call: AMDXDNA_BO_DEV_HEAP, AMDXDNA_BO_DEV
and AMDXDNA_BO_CMD. A DEV_HEAP is vmapped, so an offset equal to its
size lands the flush on the vmap guard page.

Measured on 6.18.55 on an AMD Ryzen AI 9 365 NPU, firmware 1.0.0.63,
as a non-root user with access to the accel node: unpatched, an offset
equal to the 64 MiB DEV_HEAP size oopses in drm_clflush_virt_range()
under amdxdna_drm_sync_bo_ioctl(), 2 of 2 runs; patched, the same call
returns -EINVAL, 2 of 2, and an in-bounds sync returns 0, 2 of 2.
DEV_HEAP is the type tested; DEV and CMD are by code reading.

Upstream bounds the range in amdxdna_flush_bo(), added by commit
dbc8fd7a03cb ("accel/amdxdna: Add expandable device heap support").
This applies only that check: an offset at or past the BO's end, or
an overflowing offset plus size, returns -EINVAL.

Deviations from upstream: that commit adds a feature and is too large
for stable as a whole. It calls drm_WARN() when the check rejects a BO
whose type is not AMDXDNA_BO_DEV, which userspace can trigger; this
fix does not. Upstream bounds AMDXDNA_BO_DEV by the heap chunks it
spans and flushes only the overlap, reporting no error for an offset
past the end; 6.18 has one heap per client, so this fix uses the BO's
own abo->mem.size and rejects such an offset instead. As in upstream,
a size past the BO's end is clamped, not rejected.

Built from v6.18.55 with the test system's distro-derived config,
DRM_ACCEL_AMDXDNA=m. The touched file also compiles W=1 clean.

Fixes: e252e3f3488a ("accel/amdxdna: Revise device bo creation and free")
Cc: stable@vger.kernel.org # 6.18.x
Assisted-by: LLM
Signed-off-by: Eva Crystal <0xiviel@gmail.com>
---
 drivers/accel/amdxdna/amdxdna_gem.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/accel/amdxdna/amdxdna_gem.c b/drivers/accel/amdxdna/amdxdna_gem.c
index ca747457cec7..95d04af2b993 100644
--- a/drivers/accel/amdxdna/amdxdna_gem.c
+++ b/drivers/accel/amdxdna/amdxdna_gem.c
@@ -934,6 +934,7 @@ int amdxdna_drm_sync_bo_ioctl(struct drm_device *dev,
 	struct amdxdna_drm_sync_bo *args = data;
 	struct amdxdna_gem_obj *abo;
 	struct drm_gem_object *gobj;
+	u64 end, size;
 	int ret;
 
 	gobj = drm_gem_object_lookup(filp, args->handle);
@@ -943,6 +944,13 @@ int amdxdna_drm_sync_bo_ioctl(struct drm_device *dev,
 	}
 	abo = to_xdna_obj(gobj);
 
+	if (args->offset >= abo->mem.size ||
+	    check_add_overflow(args->offset, args->size, &end)) {
+		ret = -EINVAL;
+		goto put_obj;
+	}
+	size = min(abo->mem.size, end) - args->offset;
+
 	ret = amdxdna_gem_pin(abo);
 	if (ret) {
 		XDNA_ERR(xdna, "Pin BO %d failed, ret %d", args->handle, ret);
@@ -955,7 +963,7 @@ int amdxdna_drm_sync_bo_ioctl(struct drm_device *dev,
 	if (is_import_bo(abo))
 		drm_clflush_sg(abo->base.sgt);
 	else if (abo->mem.kva)
-		drm_clflush_virt_range(abo->mem.kva + args->offset, args->size);
+		drm_clflush_virt_range(abo->mem.kva + args->offset, size);
 	else if (abo->base.pages)
 		drm_clflush_pages(abo->base.pages, gobj->size >> PAGE_SHIFT);
 	else
-- 
2.53.0