[PATCH v5.10-v6.1] drm/vmwgfx: Fix a null-ptr access in the cursor snooper

[Shivani Agarwal <shivani.agarwal@broadcom.com>]

From: Zack Rusin <zack.rusin@broadcom.com>

[ Upstream commit 5ac2c0279053a2c5265d46903432fb26ae2d0da2 ]

Check that the resource which is converted to a surface exists before
trying to use the cursor snooper on it.

vmw_cmd_res_check allows explicit invalid (SVGA3D_INVALID_ID) identifiers
because some svga commands accept SVGA3D_INVALID_ID to mean "no surface",
unfortunately functions that accept the actual surfaces as objects might
(and in case of the cursor snooper, do not) be able to handle null
objects. Make sure that we validate not only the identifier (via the
vmw_cmd_res_check) but also check that the actual resource exists before
trying to do something with it.

Fixes unchecked null-ptr reference in the snooping code.

Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Fixes: c0951b797e7d ("drm/vmwgfx: Refactor resource management")
Reported-by: Kuzey Arda Bulut <kuzeyardabulut@gmail.com>
Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Ian Forbes <ian.forbes@broadcom.com>
Link: https://lore.kernel.org/r/20250917153655.1968583-1-zack.rusin@broadcom.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[Shivani: Modified to apply on v5.10.y-v6.1.y]
Signed-off-by: Shivani Agarwal <shivani.agarwal@broadcom.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index 0d12d6af6..5d3827b5d 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -1507,6 +1507,7 @@ static int vmw_cmd_dma(struct vmw_private *dev_priv,
 		       SVGA3dCmdHeader *header)
 {
 	struct vmw_buffer_object *vmw_bo = NULL;
+	struct vmw_resource *res;
 	struct vmw_surface *srf = NULL;
 	VMW_DECLARE_CMD_VAR(*cmd, SVGA3dCmdSurfaceDMA);
 	int ret;
@@ -1542,18 +1543,24 @@ static int vmw_cmd_dma(struct vmw_private *dev_priv,
 
 	dirty = (cmd->body.transfer == SVGA3D_WRITE_HOST_VRAM) ?
 		VMW_RES_DIRTY_SET : 0;
-	ret = vmw_cmd_res_check(dev_priv, sw_context, vmw_res_surface,
-				dirty, user_surface_converter,
-				&cmd->body.host.sid, NULL);
+	ret = vmw_cmd_res_check(dev_priv, sw_context, vmw_res_surface, dirty,
+				user_surface_converter, &cmd->body.host.sid,
+				NULL);
 	if (unlikely(ret != 0)) {
 		if (unlikely(ret != -ERESTARTSYS))
 			VMW_DEBUG_USER("could not find surface for DMA.\n");
 		return ret;
 	}
 
-	srf = vmw_res_to_srf(sw_context->res_cache[vmw_res_surface].res);
+	res = sw_context->res_cache[vmw_res_surface].res;
+	if (!res) {
+		VMW_DEBUG_USER("Invalid DMA surface.\n");
+		return -EINVAL;
+	}
 
-	vmw_kms_cursor_snoop(srf, sw_context->fp->tfile, &vmw_bo->base, header);
+	srf = vmw_res_to_srf(res);
+	vmw_kms_cursor_snoop(srf, sw_context->fp->tfile, &vmw_bo->base,
+			     header);
 
 	return 0;
 }
-- 
2.40.4