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Wysocki" , Sasha Levin Subject: [PATCH 5.15.y] ACPI: CPPC: Suppress UBSAN warning caused by field misuse Date: Fri, 10 Jul 2026 09:30:16 -0400 Message-ID: <20260710133016.79831-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026070952-veto-gradually-3869@gregkh> References: <2026070952-veto-gradually-3869@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jeremy Linton [ Upstream commit 1b1acf2dada0cc3931bb2cb9ff8832edfbee46a1 ] The definition of reg->access_width changes depending on the reg->space_id type. Type ACPI_ADR_SPACE_PLATFORM_COMM uses access_width to indicate the PCC region, which can result in a UBSAN if the value is greater than 4. For example: UBSAN: shift-out-of-bounds in drivers/acpi/cppc_acpi.c:1090:9 shift exponent 32 is too large for 32-bit type 'int' CPU: 61 UID: 0 PID: 1220 Comm: (udev-worker) Not tainted 7.0.10-201.fc44.aarch64 #1 PREEMPT(lazy) Hardware name: To be filled by O.E.M. Call trace: ...(trimming) ubsan_epilogue+0x10/0x48 __ubsan_handle_shift_out_of_bounds+0xdc/0x1e0 cpc_write+0x4d0/0x670 cppc_set_perf+0x18c/0x490 cppc_cpufreq_cpu_init+0x1c8/0x380 [cppc_cpufreq] ... (trimming) Lets fix this by validating the region type, as well as whether access_width has a value. Then since we are returning bit_width directly for ACPI_ADR_SPACE_PLATFORM_COMM, drop the code correcting the size. Fixes: 2f4a4d63a193 ("ACPI: CPPC: Use access_width over bit_width for system memory accesses") Signed-off-by: Jeremy Linton Tested-by: Jarred White Reviewed-by: Jarred White Reviewed-by: Easwar Hariharan Cc: All applicable Link: https://patch.msgid.link/20260601235808.1113137-1-jeremy.linton@arm.com Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin --- drivers/acpi/cppc_acpi.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index f86e68863a24ae..30c8799b1a6a8f 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -161,8 +161,13 @@ show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_freq); show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, reference_perf); show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time); -/* Check for valid access_width, otherwise, fallback to using bit_width */ -#define GET_BIT_WIDTH(reg) ((reg)->access_width ? (8 << ((reg)->access_width - 1)) : (reg)->bit_width) +/* + * PCC reuses the access_width field as the subspace id, so only decode access + * size for non-PCC registers. Otherwise, use the bit_width. + */ +#define GET_BIT_WIDTH(reg) (((reg)->access_width && \ + (reg)->space_id != ACPI_ADR_SPACE_PLATFORM_COMM) ? \ + (8 << ((reg)->access_width - 1)) : (reg)->bit_width) /* Shift and apply the mask for CPC reads/writes */ #define MASK_VAL_READ(reg, val) (((val) >> (reg)->bit_offset) & \ @@ -970,7 +975,6 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val) * by the bit width field; the access size is used to indicate * the PCC subspace id. */ - size = reg->bit_width; vaddr = GET_PCC_VADDR(reg->address, pcc_ss_id); } else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) @@ -1030,7 +1034,6 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val) * by the bit width field; the access size is used to indicate * the PCC subspace id. */ - size = reg->bit_width; vaddr = GET_PCC_VADDR(reg->address, pcc_ss_id); } else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) -- 2.53.0