From: Arnd Bergmann <arnd@xxxxxxxx>
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 <arnd@xxxxxxxx>
---
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;
--
2.39.2
