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([2001:41d0:303:db6b::]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fcd507c78sm22132f8f.54.2026.11.03.10.50.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Nov 2026 10:50:27 -0800 (PST) From: Tristan Madani To: Marius Cristea , Jonathan Cameron Cc: David Lechner , Nuno Sa , Andy Shevchenko , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, tristan@talencesecurity.com Subject: [PATCH v7] iio: adc: pac1934: validate ACPI _DSM return type and bounds Date: Tue, 3 Nov 2026 18:50:26 +0000 Message-ID: <20261103185026.3139023-1-tristmd@gmail.com> X-Mailer: git-send-email 2.47.3 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Tristan Madani pac1934_acpi_parse_channel_config() calls acpi_evaluate_dsm() four times to read channel configuration but does not validate the returned object type or array bounds: 1. No check that the returned object is ACPI_TYPE_PACKAGE. If firmware returns a different type, accessing rez->package.count and rez->package.elements on a non-package object produces unpredictable values. 2. The loop bounds use rez->package.count directly without capping to PAC1934_MAX_NUM_CHANNELS (4). A package with more elements than expected causes writes past the fixed-size labels[], shunts[], and active_channels[] arrays. 3. The bipolar and sample rate DSM calls access elements[0] without verifying package.count >= 1. Use acpi_evaluate_dsm_typed() with ACPI_TYPE_PACKAGE to validate the return type at evaluation time. Cap loop iterations to PAC1934_MAX_NUM_CHANNELS, and verify package count >= 1 before accessing elements[0]. Reviewed-by: Marius Cristea Signed-off-by: Tristan Madani --- Changes in v7: - Round package.count to pairs with & ~1 inside min() and simplify loop condition from i + 1 < count to i < count, per Andy Shevchenko Changes in v6: - Replace min_t() with min(), per Andy Shevchenko Changes in v5: - Keep existing declaration order, only add new 'count' variable, per Andy Shevchenko - Replace (count & ~1u) with min() cap and i + 1 < count loop bound to avoid unsigned literal question, per Andy Shevchenko Changes in v4: - Reorder variable declarations to reverse xmas tree, per Andy Shevchenko - Drop casts from min() parameters, per Andy Shevchenko Changes in v3: - Use acpi_evaluate_dsm_typed() instead of manual type checks, per Andy Shevchenko - Use (count & ~1u) for the name+mohm loop bound to ensure pairs are complete, per Andy Shevchenko - Drop Fixes: and Cc: stable tags since this is hardening rather than a fix for a specific regression, per Jonathan Cameron drivers/iio/adc/pac1934.c | 31 +++++++++++++++++++++++++------ 1 file changed, 25 insertions(+), 6 deletions(-) diff --git a/drivers/iio/adc/pac1934.c b/drivers/iio/adc/pac1934.c index 5e901ab25c8e8..fcdfe5f3b9190 100644 --- a/drivers/iio/adc/pac1934.c +++ b/drivers/iio/adc/pac1934.c @@ -1094,6 +1094,7 @@ static int pac1934_acpi_parse_channel_config(struct i2c_client *client, union acpi_object *rez; struct device *dev = &client->dev; unsigned short bi_dir_mask; + unsigned int count; int idx, i; guid_t guid; @@ -1101,11 +1102,14 @@ static int pac1934_acpi_parse_channel_config(struct i2c_client *client, guid_parse(PAC1934_DSM_UUID, &guid); - rez = acpi_evaluate_dsm(handle, &guid, 0, PAC1934_ACPI_GET_NAMES_AND_MOHMS_VALS, NULL); + rez = acpi_evaluate_dsm_typed(handle, &guid, 0, + PAC1934_ACPI_GET_NAMES_AND_MOHMS_VALS, + NULL, ACPI_TYPE_PACKAGE); if (!rez) return -EINVAL; - for (i = 0; i < rez->package.count; i += 2) { + count = min(rez->package.count & ~1, PAC1934_MAX_NUM_CHANNELS * 2); + for (i = 0; i < count; i += 2) { idx = i / 2; info->labels[idx] = devm_kmemdup(dev, rez->package.elements[i].string.pointer, @@ -1122,7 +1126,9 @@ static int pac1934_acpi_parse_channel_config(struct i2c_client *client, ACPI_FREE(rez); - rez = acpi_evaluate_dsm(handle, &guid, 1, PAC1934_ACPI_GET_UOHMS_VALS, NULL); + rez = acpi_evaluate_dsm_typed(handle, &guid, 1, + PAC1934_ACPI_GET_UOHMS_VALS, + NULL, ACPI_TYPE_PACKAGE); if (!rez) { /* * initializing with default values @@ -1133,7 +1139,8 @@ static int pac1934_acpi_parse_channel_config(struct i2c_client *client, return 0; } - for (i = 0; i < rez->package.count; i++) { + count = min(rez->package.count, PAC1934_MAX_NUM_CHANNELS); + for (i = 0; i < count; i++) { idx = i; info->shunts[idx] = rez->package.elements[i].integer.value; info->active_channels[idx] = (info->shunts[idx] != 0); @@ -1141,9 +1148,15 @@ static int pac1934_acpi_parse_channel_config(struct i2c_client *client, ACPI_FREE(rez); - rez = acpi_evaluate_dsm(handle, &guid, 1, PAC1934_ACPI_GET_BIPOLAR_SETTINGS, NULL); + rez = acpi_evaluate_dsm_typed(handle, &guid, 1, + PAC1934_ACPI_GET_BIPOLAR_SETTINGS, + NULL, ACPI_TYPE_PACKAGE); if (!rez) return -EINVAL; + if (rez->package.count < 1) { + ACPI_FREE(rez); + return -EINVAL; + } bi_dir_mask = rez->package.elements[0].integer.value; info->bi_dir[0] = ((bi_dir_mask & (1 << 3)) | (bi_dir_mask & (1 << 7))) != 0; @@ -1153,9 +1166,15 @@ static int pac1934_acpi_parse_channel_config(struct i2c_client *client, ACPI_FREE(rez); - rez = acpi_evaluate_dsm(handle, &guid, 1, PAC1934_ACPI_GET_SAMP, NULL); + rez = acpi_evaluate_dsm_typed(handle, &guid, 1, + PAC1934_ACPI_GET_SAMP, + NULL, ACPI_TYPE_PACKAGE); if (!rez) return -EINVAL; + if (rez->package.count < 1) { + ACPI_FREE(rez); + return -EINVAL; + } info->sample_rate_value = rez->package.elements[0].integer.value; -- 2.47.3