linux-kernel - Re: linux-next: build failure after merge of the block tree

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Message-ID: <521f2cf0-45c4-4e20-be36-aded868edaf9@sirena.org.uk>
Date: Fri, 23 Jan 2026 19:34:01 +0000
From: Mark Brown <broonie@...nel.org>
To: Jens Axboe <axboe@...nel.dk>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the block tree

On Fri, Jan 23, 2026 at 11:00:55AM -0700, Jens Axboe wrote:
> On 1/23/26 10:42 AM, Mark Brown wrote:

> >     inlined from 'io_uring_populate_bpf_ctx' at /tmp/next/build/io_uring/bpf_filter.c:33:2:
> > /tmp/next/build/include/linux/fortify-string.h:480:25: 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]
> >   480 |                         __write_overflow_field(p_size_field, size);
> >       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...

> memset(bctx->pad, 0, sizeof(bctx->pad) + sizeof(bctx->resv));

> which should clear from offset 10 (start of pad) for a total of 6 + 48
> bytes, which is 54 bytes. The size of the struct is 64b.

I think so, it's checking that you're not overflowing the field you
specified rather than the struct containing the field.

> I guess the part it doesn't like is that it thinks we're clearing the
> pad field, which would of course be way overwriting it. Guess we can do
> something ala:

> memset((void *) bctx + offsetof(struct io_uring_bpf_ctx, pad), 0,
> 	sizeof(bctx->pad) + sizeof(bctx->resv));

> to make it happier.

Lovely.

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