Re: [PATCH bpf v3 0/2] Fix global subprog verification context

["Kumar Kartikeya Dwivedi" <memxor@gmail.com>]

On Mon Sep 14, 2026 at 3:19 PM CEST, Kumar Kartikeya Dwivedi wrote:
> Global subprogs can be invoked in both sleepable and non-sleepable
> contexts, but are verified based on context assumptions for the program
> type as a whole and not the precise context in which they are invoked.
> Nicholas identified that this can violate verifier safety assumptions.
> Verify global subprogs once for each observed sleepability context and add
> workqueue callback regression tests.
>

By mistake, I tagged bpf tree for this one, sorry. I can respin again after a
round of feedback or let someone else decide to apply it to either tree, if this
version is landable.

> Changelog:
> ----------
> v2 -> v3
> v2: https://lore.kernel.org/bpf/20260905051224.2325381-1-memxor@gmail.com
>
>  * Clarify that globals are checked only in contexts from which they are
>    reached, with two passes only when both contexts occur. (Alexei)
>  * Implement in_sleepable_context() as !in_rcu_cs(). (Alexei, Eduard)
>  * Keep the original subprogram traversal order and repeat until all
>    called contexts have been verified. (Eduard)
>  * Explain why instruction accounting needs the saved total and why the
>    exception callback uses the main program's context. (Eduard)
>  * Rename the do_check_common() parameter to is_sleepable. (BPF CI)
>  * Preserve the harmless global calls with __weak __noinline and check
>    their instruction totals across both contexts. Drop the redundant
>    task-work global RCU test and retain the review acknowledgment. (Eduard)
>
> v1 -> v2
> v1: https://lore.kernel.org/bpf/20260905034018.2095649-1-memxor@gmail.com
>
>  * Preserve the harmless global subprog calls in the positive test with
>    barrier() so LLVM cannot eliminate the intended coverage.
>  * Return zero explicitly from workqueue callbacks after global subprog calls.
>  * Document cumulative instruction accounting across verification contexts.
>  * Fix BPF multi-line comment formatting.
>
> Kumar Kartikeya Dwivedi (2):
>   bpf: Verify global subprogs in each sleepability context
>   selftests/bpf: Test global subprog callback contexts
>
>  include/linux/bpf.h                           |   5 +-
>  kernel/bpf/verifier.c                         |  71 ++++++------
>  .../bpf/progs/verifier_async_cb_context.c     | 106 ++++++++++++++++++
>  3 files changed, 146 insertions(+), 36 deletions(-)
>
>
> base-commit: 29fcf9ce4bbdf4cc339def776860e1c0095bca98