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

Jens Axboe
2026-01-23T18:06:45Z

On 1/23/26 11:00 AM, Jens Axboe wrote:
> On 1/23/26 10:42 AM, Mark Brown wrote:
>> Hi all,
>>
>> After merging the block tree, today's linux-next build (x86 allmodconfig)
>> failed like this:
>>
>> In file included from /tmp/next/build/include/linux/string.h:386,
>> from /tmp/next/build/include/linux/bitmap.h:13,
>> from /tmp/next/build/include/linux/cpumask.h:11,
>> from /tmp/next/build/arch/x86/include/asm/paravirt.h:21,
>> from /tmp/next/build/arch/x86/include/asm/cpuid/api.h:57,
>> from /tmp/next/build/arch/x86/include/asm/processor.h:19,
>> from /tmp/next/build/include/linux/sched.h:13,
>> from /tmp/next/build/include/linux/io_uring.h:5,
>> from /tmp/next/build/io_uring/bpf_filter.c:7:
>> In function 'fortify_memset_chk',
>> 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);
>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> cc1: all warnings being treated as errors
>>
>> Caused by commit
>>
>> f1e3672e49e2c (io_uring: add support for BPF filtering for opcode restrictions)
>
> Huh, that am I missing here? The struct looks as follows:
>
> struct io_uring_bpf_ctx {
> __u64 user_data;
> __u8 opcode;
> __u8 sqe_flags;
> __u8 pad[6];
> union {
> __u64 resv[6];
> struct {
> __u32 family;
> __u32 type;
> __u32 protocol;
> } socket;
> struct {
> __u64 flags;
> __u64 mode;
> __u64 resolve;
> } open;
> };
> };
>
> and the offending line is:
>
> 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 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.

Folded that in and pushed it out, should be happy for you now. I wonder
if we have a helper for that...

--
Jens Axboe