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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: 542f25a944 ("HID: hyperv: Replace one-element array with flexible-array member")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20230705140242.844167-1-arnd@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
This commit is contained in:
Arnd Bergmann 2023-07-05 16:02:24 +02:00 committed by Benjamin Tissoires
parent f9abdcc617
commit 5f151364b1
1 changed files with 4 additions and 6 deletions
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10
drivers/hid/hid-hyperv.c
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@ -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;