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Mon, 04 May 2026 16:35:06 -0700 (PDT) Received: from node ([202.47.63.86]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a822bf3ffsm390071835e9.7.2026.05.04.16.35.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2026 16:35:05 -0700 (PDT) From: Muhammad Bilal To: greybus-dev@lists.linaro.org, linux-staging@lists.linux.dev Cc: vireshk@kernel.org, johan@kernel.org, elder@kernel.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Muhammad Bilal Subject: [PATCH v1] greybus: authentication: validate CAP response payload size Date: Mon, 4 May 2026 19:33:28 -0400 Message-ID: <20260504233328.7409-1-meatuni001@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit cap_get_ims_certificate() and cap_authenticate() copy variable-length response data directly into fixed-size UAPI buffers using the untrusted op->response->payload_size value without any bounds checks. A malicious or compromised Greybus endpoint can return an oversized certificate or signature payload, causing a kernel heap overflow. Fix both functions by: - Rejecting responses shorter than sizeof(*response) with -EPROTO. - Rejecting payloads exceeding CAP_CERTIFICATE_MAX_SIZE (1600) or CAP_SIGNATURE_MAX_SIZE (320) with -EMSGSIZE. - Copying only the validated size into the UAPI buffer. Fixes: e3eda54d0b5f ("greybus: Add Component Authentication Protocol support") Signed-off-by: Muhammad Bilal --- drivers/staging/greybus/authentication.c | 34 +++++++++++++++++++++--- 1 file changed, 30 insertions(+), 4 deletions(-) diff --git a/drivers/staging/greybus/authentication.c b/drivers/staging/greybus/authentication.c index 97b9937bb..103cc15d2 100644 --- a/drivers/staging/greybus/authentication.c +++ b/drivers/staging/greybus/authentication.c @@ -109,6 +109,7 @@ static int cap_get_ims_certificate(struct gb_cap *cap, u32 class, u32 id, struct gb_cap_get_ims_certificate_request *request; struct gb_cap_get_ims_certificate_response *response; size_t max_size = gb_operation_get_payload_size_max(connection); + size_t cert_size; struct gb_operation *op; int ret; @@ -131,9 +132,21 @@ static int cap_get_ims_certificate(struct gb_cap *cap, u32 class, u32 id, } response = op->response->payload; + + if (op->response->payload_size < sizeof(*response)) { + ret = -EPROTO; + goto done; + } + + cert_size = op->response->payload_size - sizeof(*response); + if (cert_size > CAP_CERTIFICATE_MAX_SIZE) { + ret = -EMSGSIZE; + goto done; + } + *result = response->result_code; - *size = op->response->payload_size - sizeof(*response); - memcpy(certificate, response->certificate, *size); + *size = (u32)cert_size; + memcpy(certificate, response->certificate, cert_size); done: gb_operation_put(op); @@ -148,6 +161,7 @@ static int cap_authenticate(struct gb_cap *cap, u32 auth_type, u8 *uid, struct gb_cap_authenticate_request *request; struct gb_cap_authenticate_response *response; size_t max_size = gb_operation_get_payload_size_max(connection); + size_t sig_size; struct gb_operation *op; int ret; @@ -170,10 +184,22 @@ static int cap_authenticate(struct gb_cap *cap, u32 auth_type, u8 *uid, } response = op->response->payload; + + if (op->response->payload_size < sizeof(*response)) { + ret = -EPROTO; + goto done; + } + + sig_size = op->response->payload_size - sizeof(*response); + if (sig_size > CAP_SIGNATURE_MAX_SIZE) { + ret = -EMSGSIZE; + goto done; + } + *result = response->result_code; - *signature_size = op->response->payload_size - sizeof(*response); + *signature_size = (u32)sig_size; memcpy(auth_response, response->response, sizeof(response->response)); - memcpy(signature, response->signature, *signature_size); + memcpy(signature, response->signature, sig_size); done: gb_operation_put(op); -- 2.54.0