Re: [PATCH] firmware: arm_ffa: Fix warning caused by export_uuid()

[Gavin Shan]

On 10/14/24 8:08 PM, Sudeep Holla wrote:
> On Mon, Oct 14, 2024 at 10:47:24AM +1000, Gavin Shan wrote:
> > Run into build warning caused by export_uuid() where the UUID's
> > length exceeds that of ffa_value_t::a2, as the following warning
> > messages indicate.
> >
> > In function ‘fortify_memcpy_chk’,
> > inlined from ‘export_uuid’ at ./include/linux/uuid.h:88:2,
> > inlined from ‘ffa_msg_send_direct_req2’ at drivers/firmware/arm_ffa/driver.c:488:2:
> > ./include/linux/fortify-string.h:571:25: 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]
> > 571 |                         __write_overflow_field(p_size_field, size);
> >      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Fix it by not passing a plain buffer to memcpy() to avoid the overflow
> > and underflow warning, similar to what have been done to copy over the
> > struct ffa_send_direct_data2.
>
> Are you observing this just on the upstream or -next as well? There is a
> fix in the -next which I haven't sent to soc team yet, will do so soon.

I just tried the upstream when the patch was posted. I just have a try with -next
and similar error exists.

[root@nvidia-grace-hopper-01 linux-next]# git remote -v
origin	git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git (fetch)
origin	git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git (push)
[root@nvidia-grace-hopper-01 linux-next]# make W=1 drivers/firmware/arm_ffa/driver.o
   :
In function ‘fortify_memcpy_chk’,
    inlined from ‘ffa_msg_send_direct_req2’ at drivers/firmware/arm_ffa/driver.c:504:3:
./include/linux/fortify-string.h:580:25: error: call to ‘__read_overflow2_field’ declared with attribute warning: \
detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning]
  580 |                         __read_overflow2_field(q_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors


Part of the changes included this patch is still needed by -next. Could you please
squeeze the changes to that one to be pulled?

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 8dd81db9b071..b14cbdae94e8 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -501,7 +501,7 @@ static int ffa_msg_send_direct_req2(u16 src_id, u16 dst_id, const uuid_t *uuid,
                return ffa_to_linux_errno((int)ret.a2);
 
        if (ret.a0 == FFA_MSG_SEND_DIRECT_RESP2) {
-               memcpy(data, &ret.a4, sizeof(*data));
+               memcpy(data, (void *)&ret + offsetof(ffa_value_t, a4), sizeof(*data));
                return 0;
        }

Thanks,
Gavin