Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues: - [High] Uncapped request_bw is assigned to allocated_bw, causing an oversized value that leads to an integer underflow during bandwidth validation. -- --- Patch [1]: [PATCH] drm/amd/display: fix division by zero in get_estimated_bw() --- commit d3870b3b2da2897f934f4033da62b969b6443914 Author: Hari Mishal <[email protected]> drm/amd/display: fix division by zero in get_estimated_bw() This commit fixes a division by zero in get_estimated_bw() by returning 0 if bw_granularity is zero. This prevents a crash when a connected DPIA device reports an estimated bandwidth change before reporting a capability change. > link_dpia_send_bw_alloc_request() already guards the same > bw_granularity division; add the identical guard here rather than > introducing a new pattern. [Severity: High] This is a pre-existing issue, but since the commit message references link_dpia_send_bw_alloc_request(), I noticed a potential integer underflow issue involving allocated_bw. In link_dpia_send_bw_alloc_request(), the uncapped request_bw variable is assigned to allocated_bw: drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_dpia_bw.c:link_dpia_send_bw_alloc_request() { ... temp = req_bw * link->dpia_bw_alloc_config.bw_granularity; request_reg_val = temp / Kbps_TO_Gbps; if (temp % Kbps_TO_Gbps) ++request_reg_val; } link->dpia_bw_alloc_config.allocated_bw = request_bw; ... } Later, in link_dpia_validate_dp_tunnel_bandwidth(), remaining_bw is calculated using unsigned 32-bit subtraction: drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_dpia_bw.c:link_dpia_validate_dp_tunnel_bandwidth() { ... if (router_sets[j].cm_id == dp_tunnel_settings->cm_id) { uint32_t remaining_bw = dp_tunnel_settings->estimated_bw - dp_tunnel_settings->allocated_bw; ... } If a connected DPIA display requests more bandwidth than estimated, allocated_bw will be strictly greater than estimated_bw. Could this cause the subtraction to underflow to an extremely large positive value (~4.29 billion), thereby bypassing the subsequent capacity checks (required_bw > total_bw) and allowing illegal configurations that oversubscribe the DP tunnel? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
