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Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Paulo Miguel Almeida , Michael Kelley , Dawei Li , Yang Yingliang , =?utf-8?q?Thomas_Wei=C3=9Fschuh?= , linux-hyperv@vger.kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] HID: hyperv: avoid struct memcpy overrun warning Date: Wed, 5 Jul 2023 16:02:24 +0200 Message-Id: <20230705140242.844167-1-arnd@kernel.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1770590704313695183?= X-GMAIL-MSGID: =?utf-8?q?1770590704313695183?= From: Arnd Bergmann A previous patch addressed the fortified memcpy warning for most builds, but I still see this one with gcc-9: In file included from include/linux/string.h:254, from drivers/hid/hid-hyperv.c:8: In function 'fortify_memcpy_chk', inlined from 'mousevsc_on_receive' at drivers/hid/hid-hyperv.c:272:3: include/linux/fortify-string.h:583:4: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] 583 | __write_overflow_field(p_size_field, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ My guess is that the WARN_ON() itself is what confuses gcc, so it no longer sees that there is a correct range check. Rework the code in a way that helps readability and avoids the warning. Fixes: 542f25a944715 ("HID: hyperv: Replace one-element array with flexible-array member") Signed-off-by: Arnd Bergmann Reviewed-by: Michael Kelley --- drivers/hid/hid-hyperv.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/hid/hid-hyperv.c b/drivers/hid/hid-hyperv.c index 49d4a26895e76..f33485d83d24f 100644 --- a/drivers/hid/hid-hyperv.c +++ b/drivers/hid/hid-hyperv.c @@ -258,19 +258,17 @@ static void mousevsc_on_receive(struct hv_device *device, switch (hid_msg_hdr->type) { case SYNTH_HID_PROTOCOL_RESPONSE: + len = struct_size(pipe_msg, data, pipe_msg->size); + /* * While it will be impossible for us to protect against * malicious/buggy hypervisor/host, add a check here to * ensure we don't corrupt memory. */ - if (struct_size(pipe_msg, data, pipe_msg->size) - > sizeof(struct mousevsc_prt_msg)) { - WARN_ON(1); + if (WARN_ON(len > sizeof(struct mousevsc_prt_msg))) break; - } - memcpy(&input_dev->protocol_resp, pipe_msg, - struct_size(pipe_msg, data, pipe_msg->size)); + memcpy(&input_dev->protocol_resp, pipe_msg, len); complete(&input_dev->wait_event); break;