Re: [PATCH bpf-next v3] bpf: allow ksock connect/send calls from wq

[Mahe Tardy <mahe.tardy@gmail.com>]

On Wed, Oct 14, 2026 at 09:26:39AM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] bpf: selftests: u64 map key mismatch causes ksock_wq failure on big-endian
> --
> 
> commit e40a8841b185289348c211758c8754c0959c28bd
> Author: Mahe Tardy <mahe.tardy@gmail.com>
> 
> bpf: allow ksock connect/send calls from wq
> 
> This commit relaxes the constraint on not using the workqueues for ksock 
> connect() or send() kfuncs. It also updates the selftests to verify this 
> behavior.
> 
> > diff --git a/tools/testing/selftests/bpf/progs/ksock_wq.c b/tools/testing/selftests/bpf/progs/ksock_wq.c
> > index 16a1873d132ed..290736e219e1d 100644
> > --- a/tools/testing/selftests/bpf/progs/ksock_wq.c
> > +++ b/tools/testing/selftests/bpf/progs/ksock_wq.c
> > @@ -14,15 +15,19 @@ struct ksock_wq_value {
> >  
> >  struct {
> >  	__uint(type, BPF_MAP_TYPE_ARRAY);
> > -	__uint(max_entries, 1);
> > +	__uint(max_entries, 2);
> >  	__type(key, u32);
> >  	__type(value, struct ksock_wq_value);
> >  } work_map SEC(".maps");
> 
> [ ... ]
> 
> > @@ -43,20 +73,40 @@ static int ksock_wq_callback(void *map, int *key, void *value)
> >  SEC("syscall")
> >  int ksock_wq_start(void *ctx)
> >  {
> > +	struct bpf_ksock_create_opts opts = {
> > +		.family = AF_INET,
> > +		.type = SOCK_DGRAM,
> > +		.protocol = IPPROTO_UDP,
> > +	};
> >  	struct ksock_wq_value *value;
> > -	u32 key = 0;
> > -	int err;
> > +	struct bpf_ksock *ks;
> > +	u64 key = 0;
> > +	int err = 0;
> >  
> > -	value = bpf_map_lookup_elem(&work_map, &key);
> > -	if (!value)
> > -		return -ENOENT;
> > -	err = bpf_wq_init(&value->work, &work_map, 0);
> > -	if (err)
> > +	ks = bpf_ksock_create(&opts, sizeof(opts), &err);
> > +	if (!ks)
> >  		return err;
> > -	err = bpf_wq_set_callback(&value->work, ksock_wq_callback, 0);
> > +	err = ksock_ctx_insert(ks);
> >  	if (err)
> >  		return err;
> > -	return bpf_wq_start(&value->work, 0);
> > +	for (key = 0; key < 2; key++) {
> > +		value = bpf_map_lookup_elem(&work_map, &key);
> 
> [Severity: Medium]
> Could this cause failures on big-endian systems?
> 
> In ksock_wq_start(), the key variable was changed from u32 to u64, but
> work_map is defined as a BPF_MAP_TYPE_ARRAY with a u32 key.
> 
> When &key is passed to bpf_map_lookup_elem(), big-endian systems will read
> the first 4 bytes of the u64 (which will be 0 for both iterations in the
> loop).
> 
> This would cause the lookup to return the element at index 0 multiple times,
> leading to double-initialization of the same workqueue via bpf_wq_init()
> and subsequent failures.

Oh no :facepalm:, I sent the v2 again instead of the v3 with the u32
change... Sorry for the spam, I'll send the proper v3 as v4 in a while
to avoid sending too many emails on the same patchset at once.

> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20261014091450.19107-1-mahe.tardy@gmail.com?part=1