From: Gabe Teeger Date: Mon, 16 Mar 2026 14:41:27 +0000 (-0400) Subject: drm/amd/display: Fix bounds checking in dml2_0 clock table array X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1f991ceb2c0bd37214387a645a1d3a260d423f7d;p=thirdparty%2Flinux.git drm/amd/display: Fix bounds checking in dml2_0 clock table array [Why] Multiple locations in dml2_0 used num_clk_values-1 as array index without checking if num_clk_values > 0. When num_clk_values is 0, this results in accessing array index -1, which wraps to 255 for unsigned types, causing out-of-bounds memory access and potential crashes. [How] Add proper bounds checking using ternary operators to guard all num_clk_values-1 array accesses. When num_clk_values is 0, return 0 as fallback value instead of accessing invalid memory. This prevents buffer overflows while maintaining backward compatibility and provides sensible default behavior for empty clock tables. Reviewed-by: Dillon Varone Signed-off-by: Gabe Teeger Signed-off-by: Chuanyu Tseng Signed-off-by: Alex Deucher --- diff --git a/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_dpmm/dml2_dpmm_dcn4.c b/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_dpmm/dml2_dpmm_dcn4.c index d17e59d684fd1..ab0b4a4b5d65f 100644 --- a/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_dpmm/dml2_dpmm_dcn4.c +++ b/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_dpmm/dml2_dpmm_dcn4.c @@ -279,6 +279,26 @@ static bool round_up_and_copy_to_next_dpm(unsigned long min_value, unsigned long bool result = false; int index = 0; + /* Guard against empty clock tables (e.g. DTBCLK on DCN42B where the + * clock is tied off and num_clk_values == 0). Without this check the + * else-if branch below would evaluate + * clk_values_khz[num_clk_values - 1] with num_clk_values == 0, which + * wraps the unsigned char index to 255 — a 235-element out-of-bounds + * read on an array of DML_MAX_CLK_TABLE_SIZE (20) entries. + * + * Semantic: if the clock doesn't exist on this ASIC but no frequency + * is required (min_value == 0), the request is trivially satisfied. + * If a non-zero frequency is required but the clock is absent, the + * configuration is unsupportable. + */ + if (clock_table->num_clk_values == 0) { + if (min_value == 0) { + *rounded_value = 0; + return true; + } + return false; + } + if (clock_table->num_clk_values > 2) { while (index < clock_table->num_clk_values && clock_table->clk_values_khz[index] < min_value) index++; diff --git a/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn4.c b/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn4.c index a265f254152c7..eab13e1c96fd5 100644 --- a/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn4.c +++ b/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn4.c @@ -178,9 +178,12 @@ static bool build_min_clock_table(const struct dml2_soc_bb *soc_bb, struct dml2_ min_table->max_clocks_khz.dispclk = soc_bb->clk_table.dispclk.clk_values_khz[soc_bb->clk_table.dispclk.num_clk_values - 1]; min_table->max_clocks_khz.dppclk = soc_bb->clk_table.dppclk.clk_values_khz[soc_bb->clk_table.dppclk.num_clk_values - 1]; - min_table->max_clocks_khz.dscclk = soc_bb->clk_table.dscclk.clk_values_khz[soc_bb->clk_table.dscclk.num_clk_values - 1]; - min_table->max_clocks_khz.dtbclk = soc_bb->clk_table.dtbclk.clk_values_khz[soc_bb->clk_table.dtbclk.num_clk_values - 1]; - min_table->max_clocks_khz.phyclk = soc_bb->clk_table.phyclk.clk_values_khz[soc_bb->clk_table.phyclk.num_clk_values - 1]; + min_table->max_clocks_khz.dscclk = (soc_bb->clk_table.dscclk.num_clk_values > 0) ? + soc_bb->clk_table.dscclk.clk_values_khz[soc_bb->clk_table.dscclk.num_clk_values - 1] : 0; + min_table->max_clocks_khz.dtbclk = (soc_bb->clk_table.dtbclk.num_clk_values > 0) ? + soc_bb->clk_table.dtbclk.clk_values_khz[soc_bb->clk_table.dtbclk.num_clk_values - 1] : 0; + min_table->max_clocks_khz.phyclk = (soc_bb->clk_table.phyclk.num_clk_values > 0) ? + soc_bb->clk_table.phyclk.clk_values_khz[soc_bb->clk_table.phyclk.num_clk_values - 1] : 0; min_table->max_ss_clocks_khz.dispclk = (unsigned int)((double)min_table->max_clocks_khz.dispclk / (1.0 + soc_bb->dcn_downspread_percent / 100.0)); min_table->max_ss_clocks_khz.dppclk = (unsigned int)((double)min_table->max_clocks_khz.dppclk / (1.0 + soc_bb->dcn_downspread_percent / 100.0)); diff --git a/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn42.c b/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn42.c index 1f67cbc2c2366..3eaeff39ee792 100644 --- a/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn42.c +++ b/drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_mcg/dml2_mcg_dcn42.c @@ -54,9 +54,12 @@ static bool build_min_clock_table(const struct dml2_soc_bb *soc_bb, struct dml2_ min_table->max_clocks_khz.dispclk = soc_bb->clk_table.dispclk.clk_values_khz[soc_bb->clk_table.dispclk.num_clk_values - 1]; min_table->max_clocks_khz.dppclk = soc_bb->clk_table.dppclk.clk_values_khz[soc_bb->clk_table.dppclk.num_clk_values - 1]; - min_table->max_clocks_khz.dscclk = soc_bb->clk_table.dscclk.clk_values_khz[soc_bb->clk_table.dscclk.num_clk_values - 1]; - min_table->max_clocks_khz.dtbclk = soc_bb->clk_table.dtbclk.clk_values_khz[soc_bb->clk_table.dtbclk.num_clk_values - 1]; - min_table->max_clocks_khz.phyclk = soc_bb->clk_table.phyclk.clk_values_khz[soc_bb->clk_table.phyclk.num_clk_values - 1]; + min_table->max_clocks_khz.dscclk = (soc_bb->clk_table.dscclk.num_clk_values > 0) ? + soc_bb->clk_table.dscclk.clk_values_khz[soc_bb->clk_table.dscclk.num_clk_values - 1] : 0; + min_table->max_clocks_khz.dtbclk = (soc_bb->clk_table.dtbclk.num_clk_values > 0) ? + soc_bb->clk_table.dtbclk.clk_values_khz[soc_bb->clk_table.dtbclk.num_clk_values - 1] : 0; + min_table->max_clocks_khz.phyclk = (soc_bb->clk_table.phyclk.num_clk_values > 0) ? + soc_bb->clk_table.phyclk.clk_values_khz[soc_bb->clk_table.phyclk.num_clk_values - 1] : 0; min_table->max_ss_clocks_khz.dispclk = (unsigned int)((double)min_table->max_clocks_khz.dispclk / (1.0 + soc_bb->dcn_downspread_percent / 100.0)); min_table->max_ss_clocks_khz.dppclk = (unsigned int)((double)min_table->max_clocks_khz.dppclk / (1.0 + soc_bb->dcn_downspread_percent / 100.0));