On Tue, Sep 10, 2024, at 2:07 PM, Daniel Xu wrote:
On Tue, Sep 10, 2024 at 01:41:41PM GMT, Andrii Nakryiko wrote:
On Tue, Sep 10, 2024 at 11:36 AM Alexei Starovoitov
[...]
Also, Daniel, can you please make sure that dynptr we return for each sample is read-only? We shouldn't let consumer BPF program ability to corrupt ringbuf record headers (accidentally or otherwise).
Sure.
So the sample is not read-only. But I think prog is prevented from messing with header regardless.
__bpf_user_ringbuf_peek() returns sample past the header:
*sample = (void *)((uintptr_t)rb->data + (uintptr_t)((cons_pos + BPF_RINGBUF_HDR_SZ) & rb->mask));
dynptr is initialized with the above ptr:
bpf_dynptr_init(&dynptr, sample, BPF_DYNPTR_TYPE_LOCAL, 0, size);
So I don't think there's a way for the prog to access the header thru the dynptr.
Thanks, Daniel