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([2409:4090:20a4:5c0c:c48f:19c:3b62:c592]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23de4343e48sm22862495ad.190.2025.07.10.08.10.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Jul 2025 08:10:33 -0700 (PDT) Message-ID: <8af20362-2ec8-4d56-b5ea-fc226775c37a@gmail.com> Date: Thu, 10 Jul 2025 20:40:30 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] firewire: ohci: Initialize payload_bus to avoid uninitialized use warning To: linux1394-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20250710073906.24105-1-purvayeshi550@gmail.com> <20250710125227.GA25686@workstation.local> Content-Language: en-US From: Purva Yeshi In-Reply-To: <20250710125227.GA25686@workstation.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/07/25 18:22, Takashi Sakamoto wrote: > Hi, > > On Thu, Jul 10, 2025 at 01:09:06PM +0530, Purva Yeshi wrote: >> Fix Smatch-detected error: >> drivers/firewire/ohci.c:1514 at_context_queue_packet() >> error: uninitialized symbol 'payload_bus'. >> >> Smatch reports a potential uninitialized use of 'payload_bus' in >> at_context_queue_packet(). If packet->payload_length is zero, the >> variable may not be set before reaching the dma_unmap_single() call, >> which could lead to undefined behavior. >> >> Initialize 'payload_bus' to 0 to ensure it has a defined value in all >> code paths, preventing any uninitialized access. >> >> Signed-off-by: Purva Yeshi > > In my opinion, we should pay enough attention to the value of > 'packet->payload_mapped' variable when considering the issue. Hi Takashi, Thank you for your review. The change was mainly to address the Smatch warning, which reports a possible uninitialized use. While it might not be a real issue in practice. > > ``` > $ cat -n drivers/firewire/ohci.c > ... > 1385 static int at_context_queue_packet(struct context *ctx, > 1386 struct fw_packet *packet) > 1387 { > 1388 struct fw_ohci *ohci = ctx->ohci; > 1389 dma_addr_t d_bus, payload_bus; > ... > 1474 if (packet->payload_length > 0) { > 1475 if (packet->payload_length > sizeof(driver_data->inline_data)) { > 1476 payload_bus = dma_map_single(ohci->card.device, > ... > 1485 packet->payload_mapped = true; > 1486 } else { > ... > 1489 payload_bus = d_bus + 3 * sizeof(*d); > 1490 } > ... > 1496 } else { > ... > 1499 } > ... > 1506 if (ohci->generation != packet->generation) { > 1507 if (packet->payload_mapped) > 1508 dma_unmap_single(ohci->card.device, payload_bus, > 1509 packet->payload_length, DMA_TO_DEVICE); > ... > 1512 } > > Unless the variable has true, the dma_unmap_single() is never called, > thus the issue does not occur. > > > Thanks > > Takashi Sakamoto Let me know if you would prefer addressing this with a comment explaining the assumption, or if you believe it's appropriate to silence the Smatch warning in another way. Alternatively, would you recommend simply ignoring the warning in this case? Best regards, Purva Yeshi