Re: [PATCH bpf-next v12 5/8] bpf: Add syscall common attributes support for btf_load

[Leon Hwang <leon.hwang@linux.dev>]

On Mon, 20 Apr 2026 14:56:31 +0000 (UTC), bot+bpf-ci@kernel.org wrote:
>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>> index 1eb15a51c7dc..06aea4e499a1 100644
>> --- a/kernel/bpf/syscall.c
>> +++ b/kernel/bpf/syscall.c
>
> [ ... ]
>
>> @@ -6317,7 +6317,12 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
>> err = bpf_raw_tracepoint_open(&attr);
>> break;
>> case BPF_BTF_LOAD:
>> -		err = bpf_btf_load(&attr, uattr, size);
>> +		if (size >= offsetofend(union bpf_attr, btf_log_true_size))
>> +			offsetof_log_true_size = offsetof(union bpf_attr, btf_log_true_size);
>> +		err = bpf_log_attr_init(&attr_log, attr.btf_log_buf, attr.btf_log_size,
>> +					attr.btf_log_level, offsetof_log_true_size, uattr,
>> +					&attr_common, uattr_common, size_common);
>> +		err = err ?: bpf_btf_load(&attr, uattr, &attr_log);
>
> Should the log_true_size offset be set only for user space calls? In v10
> review, Andrii Nakryiko noted that log_true_size should only be set for
> user space, not kernel space calls.
>
> https://lore.kernel.org/bpf/CAEf4BzY3GA+860RODLaXqqO3j5AgJ24pmKU1yv3+gHJpy0DvNA@mail.gmail.com/
>
> The current code does not check uattr.is_kernel before setting
> offsetof_log_true_size. This could cause issues when bpf_sys_bpf() calls
> __sys_bpf() with KERNEL_BPFPTR, as it would attempt to write log_true_size
> to a kernel pointer instead of a user space pointer.
>

Not true. 'uattr.is_kernel' will be checked in copy_to_bpfptr_offset().
When write log_true_size to a kernel pointer, memcpy() will be used.

Thanks,
Leon

>> break;
>> case BPF_BTF_GET_FD_BY_ID:
>> err = bpf_btf_get_fd_by_id(&attr);
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/24672239158