Re: [PATCH bpf v3 1/2] bpf: Reject sleepable kprobe_multi programs at attach time

Kumar Kartikeya Dwivedi
2026-04-01T22:46:02Z

On Wed, 1 Apr 2026 at 21:11, Varun R Mallya <varunrmallya@gmail.com> wrote:
>
> kprobe.multi programs run in atomic/RCU context and cannot sleep.
> However, bpf_kprobe_multi_link_attach() did not validate whether the
> program being attached had the sleepable flag set, allowing sleepable
> helpers such as bpf_copy_from_user() to be invoked from a non-sleepable
> context.
>
> This causes a "sleeping function called from invalid context" splat:
>
> BUG: sleeping function called from invalid context at ./include/linux/uaccess.h:169
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1787, name: sudo
> preempt_count: 1, expected: 0
> RCU nest depth: 2, expected: 0
>
> Fix this by rejecting sleepable programs early in
> bpf_kprobe_multi_link_attach(), before any further processing.
>
> Fixes: 0dcac2725406 ("bpf: Add multi kprobe link")
> Signed-off-by: Varun R Mallya <varunrmallya@gmail.com>
> ---

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

Jiri, would be great if you can ack both patches too.