From 5f151364b1da6bd217632fd4ee8cc24eaf66a497 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 5 Jul 2023 16:02:24 +0200 Subject: [PATCH] HID: hyperv: avoid struct memcpy overrun warning 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: 542f25a94471 ("HID: hyperv: Replace one-element array with flexible-array member") Signed-off-by: Arnd Bergmann Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20230705140242.844167-1-arnd@kernel.org Signed-off-by: Benjamin Tissoires --- 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 49d4a26895e7..f33485d83d24 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;