Re: [PATCH bpf-next v2 4/6] bpf: Disallow !call_get_func_ip progs tail-calling call_get_func_ip progs
From: bot+bpf-ci@kernel.org
Date: 2026-03-02 15:53:11
Also in:
linux-kselftest, lkml, netdev
quoted hunk ↗ jump to hunk
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c
[ ... ]
quoted hunk ↗ jump to hunk
@@ -2422,11 +2423,17 @@ static bool bpf_map_owner_matches(const struct bpf_map *map, const struct bpf_prog *fp, case BPF_MAP_OWNER_MATCH_FOR_INIT: if (owner->kprobe_write_ctx != aux->kprobe_write_ctx) return false; + if (owner->call_get_func_ip != fp->call_get_func_ip) + return false; break; case BPF_MAP_OWNER_MATCH_FOR_UPDATE: if (!owner->kprobe_write_ctx && aux->kprobe_write_ctx) return false; + if (bpf_prog_has_trampoline(fp)) { + if (!owner->call_get_func_ip && fp->call_get_func_ip) + return false; + } break;
The FOR_UPDATE path correctly guards the call_get_func_ip check with
bpf_prog_has_trampoline(fp), since only trampoline-based programs
rely on the func IP stored on the trampoline stack. Kprobe programs
get func_ip from kprobe_running()->addr via bpf_get_func_ip_kprobe(),
which is independent of the trampoline.
Should the FOR_INIT path have the same bpf_prog_has_trampoline()
guard? Without it, two kprobe programs that share a prog_array will
be rejected if one calls bpf_get_func_ip() and the other does not,
even though mixing is safe for kprobes.
bpf_check_tail_call() calls this with BPF_MAP_OWNER_MATCH_FOR_INIT:
kprobe prog_a (call_get_func_ip=1) loads, references jmp_table
-> owner->call_get_func_ip = 1
kprobe prog_b (call_get_func_ip=0) loads, references same jmp_table
-> owner->call_get_func_ip != fp->call_get_func_ip
-> returns false, prog_b fails to load
Something like this would match the FOR_UPDATE scoping:
case BPF_MAP_OWNER_MATCH_FOR_INIT:
if (owner->kprobe_write_ctx != aux->kprobe_write_ctx)
return false;
if (bpf_prog_has_trampoline(fp)) {
if (owner->call_get_func_ip != fp->call_get_func_ip)
return false;
}
break;
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/22582690876
AI-authorship-score: medium
AI-authorship-explanation: The v1 selftests carried Assisted-by Codex tags, and the kernel code follows a mechanical copy-paste pattern across commits; the v2 selftests were rewritten but the overall series structure suggests AI-assisted development.
issues-found: 1
issue-severity-score: low
issue-severity-explanation: The FOR_INIT strict equality check on call_get_func_ip is missing a bpf_prog_has_trampoline() guard, causing unnecessary rejection of kprobe programs that share a prog_array with different call_get_func_ip values.