From: sashiko-bot@kernel.org
To: "Yonghong Song" <yonghong.song@linux.dev>
Cc: bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next v6 05/21] bpf: Prepare for an exception cleanup table before the CFG walk
Date: Sat, 26 Sep 2026 05:16:38 +0000 [thread overview]
Message-ID: <20260926051638.867681F00893@smtp.kernel.org> (raw)
In-Reply-To: <20260926050032.2215748-1-yonghong.song@linux.dev>
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] bpf: bpf_throw() bypasses exception_callback_subprog check skipping cleanup pads
--
commit bfb14bc84bb67f59ae10ca034e824ec0357d7d80
Author: Yonghong Song <yonghong.song@linux.dev>
bpf: Prepare for an exception cleanup table before the CFG walk
This commit introduces bpf_prepare_cleanup_exceptions() to record landing pads
for BPF-to-BPF calls and bpf_unwind() within a cleanup record's range. It
ensures the JIT supports dispatching landing pads and refuses to combine
tables with an exception callback.
> diff --git a/kernel/bpf/exception.c b/kernel/bpf/exception.c
> index b19fcbf49b7ef..1ed0370a171b7 100644
> --- a/kernel/bpf/exception.c
> +++ b/kernel/bpf/exception.c
> @@ -7,9 +7,56 @@
> #include <linux/filter.h>
> #include "exception.h"
>
> +#define verbose(env, fmt, args...) bpf_verifier_log_write(env, fmt, ##args)
> +
> BTF_ID_LIST_SINGLE(bpf_unwind_id, func, bpf_unwind)
> BTF_ID_LIST_SINGLE(bpf_unwind_resume_id, func, bpf_unwind_resume)
>
> +static void mark_call_sites(struct bpf_verifier_env *env)
> +{
> + u32 i, j;
> +
> + for (i = 0; i < env->cleanup_info_cnt; i++) {
> + struct bpf_cleanup_info *rec = &env->cleanup_info[i];
> +
> + for (j = rec->begin_off; j < rec->end_off; j++) {
> + struct bpf_insn *insn = &env->prog->insnsi[j];
> +
> + if (!bpf_pseudo_call(insn) && !bpf_is_unwind_kfunc(insn))
> + continue;
[Severity: Medium]
Since bpf_throw() is not matched here, does it skip receiving a landing pad?
If a program is loaded with .bpf_cleanup records and calls bpf_throw() without
specifying a custom exception callback, could this cause it to silently bypass
the cleanup execution during unwinding, leaking user-defined logical resources
like map-based counters?
> + env->insn_aux_data[j].cleanup_pad = rec->landing_pad_off + 1;
> + }
> + }
> +}
> +
> +int bpf_prepare_cleanup_exceptions(struct bpf_verifier_env *env)
> +{
[ ... ]
> + if (!bpf_jit_supports_cleanup_pads() || !env->prog->jit_requested) {
> + verbose(env,
> + "exception cleanup needs a JIT that can dispatch landing pads\n");
> + return -EOPNOTSUPP;
> + }
> + env->prog->jit_required = 1;
> +
> + if (env->exception_callback_subprog) {
[Severity: Medium]
Does this check the state of env->exception_callback_subprog too early?
If a later pass dynamically inserts a default exception callback, could it
bypass this restriction and result in a mix of exception cleanup tables and
bpf_throw() usage?
> + verbose(env,
> + "exception cleanup table cannot be combined with an exception callback\n");
> + return -EINVAL;
> + }
> +
> + mark_call_sites(env);
> + return 0;
> +}
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260926050006.2213110-1-yonghong.song@linux.dev?part=5
next prev parent reply other threads:[~2026-09-26 5:16 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-26 5:00 [PATCH bpf-next v6 00/21] bpf: Run exception cleanup landing pads when bpf_unwind() unwinds Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 01/21] bpf: Pack bpf_insn_aux_data flags into bit fields Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 02/21] bpf: Accept the compiler's exception cleanup table at program load Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 03/21] bpf: Add the bpf_unwind() and bpf_unwind_resume() kfuncs Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 04/21] bpf: Add lookups for exception cleanup resumes and landing pads Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 05/21] bpf: Prepare for an exception cleanup table before the CFG walk Yonghong Song
2026-09-26 5:16 ` sashiko-bot [this message]
2026-09-26 23:54 ` Yonghong Song
2026-09-27 20:39 ` bot+bpf-ci
2026-09-28 0:01 ` Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 06/21] bpf: Make exception landing pads reachable in the CFG Yonghong Song
2026-09-26 5:21 ` sashiko-bot
2026-09-27 0:02 ` Yonghong Song
2026-09-27 20:40 ` bot+bpf-ci
2026-09-28 0:12 ` Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 07/21] bpf: Resume a covered call at its landing pad Yonghong Song
2026-09-26 5:15 ` sashiko-bot
2026-09-26 8:21 ` Alexei Starovoitov
2026-09-27 0:04 ` Yonghong Song
2026-09-27 0:41 ` Yonghong Song
2026-09-27 20:40 ` bot+bpf-ci
2026-09-28 0:17 ` Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 08/21] bpf: Refuse a landing pad that does not resume Yonghong Song
2026-09-26 5:17 ` sashiko-bot
2026-09-27 3:06 ` Yonghong Song
2026-09-27 20:40 ` bot+bpf-ci
2026-09-28 0:29 ` Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 09/21] bpf: Refuse a private stack for a program with an exception cleanup table Yonghong Song
2026-09-26 5:00 ` [PATCH bpf-next v6 10/21] bpf: Dispatch cleanup pads by rewriting return addresses Yonghong Song
2026-09-27 20:40 ` bot+bpf-ci
2026-09-28 1:08 ` Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 11/21] bpf, x86: Dispatch exception cleanup pads at run time Yonghong Song
2026-09-26 5:15 ` sashiko-bot
2026-09-27 4:35 ` Yonghong Song
2026-09-27 20:39 ` bot+bpf-ci
2026-09-28 3:10 ` Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 12/21] bpf, arm64: " Yonghong Song
2026-09-26 5:14 ` sashiko-bot
2026-09-27 20:40 ` bot+bpf-ci
2026-09-26 5:01 ` [PATCH bpf-next v6 13/21] libbpf: Resolve the compiler's _Unwind_Resume to the kernel's kfunc Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 14/21] libbpf: Add cleanup_info to bpf_prog_load_opts Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 15/21] libbpf: Collect .bpf_cleanup records and pass them to the kernel Yonghong Song
2026-09-27 20:39 ` bot+bpf-ci
2026-09-28 3:28 ` Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 16/21] libbpf: Carry the exception cleanup table through the light skeleton Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 17/21] libbpf: Let the static linker carry .bpf_cleanup relocations Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 18/21] selftests/bpf: Add an end-to-end .bpf_cleanup exception test Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 19/21] selftests/bpf: Add __set_global() and __ret_global() test tags Yonghong Song
2026-09-26 5:18 ` sashiko-bot
2026-09-27 4:58 ` Yonghong Song
2026-09-27 20:24 ` bot+bpf-ci
2026-09-28 3:36 ` Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 20/21] selftests/bpf: Cover the exception cleanup shapes the chain does not reach Yonghong Song
2026-09-27 20:40 ` bot+bpf-ci
2026-09-28 3:49 ` Yonghong Song
2026-09-26 5:01 ` [PATCH bpf-next v6 21/21] selftests/bpf: Load an exception cleanup program from a light skeleton Yonghong Song
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