Re: [PATCH bpf-next v12 04/13] bpf: support fsession for bpf_session_is_return
From: bot+bpf-ci@kernel.org
Date: 2026-01-24 04:03:32
Also in:
bpf, lkml
quoted hunk ↗ jump to hunk
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 13f0a2de33b7..f7baeb8278ca 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c
[ ... ]
quoted hunk ↗ jump to hunk
@@ -3341,34 +3349,39 @@ __bpf_kfunc __u64 *bpf_session_cookie(void *ctx) __bpf_kfunc_end_defs(); -BTF_KFUNCS_START(kprobe_multi_kfunc_set_ids) +BTF_KFUNCS_START(session_kfunc_set_ids) BTF_ID_FLAGS(func, bpf_session_is_return) BTF_ID_FLAGS(func, bpf_session_cookie) -BTF_KFUNCS_END(kprobe_multi_kfunc_set_ids) +BTF_KFUNCS_END(session_kfunc_set_ids) -static int bpf_kprobe_multi_filter(const struct bpf_prog *prog, u32 kfunc_id) +static int bpf_session_filter(const struct bpf_prog *prog, u32 kfunc_id) { - if (!btf_id_set8_contains(&kprobe_multi_kfunc_set_ids, kfunc_id)) + if (!btf_id_set8_contains(&session_kfunc_set_ids, kfunc_id)) return 0; - if (!is_kprobe_session(prog) && !is_uprobe_session(prog)) + if (!is_kprobe_session(prog) && !is_uprobe_session(prog) && !is_trace_fsession(prog)) return -EACCES;
The filter now allows fsession programs to call both bpf_session_is_return()
and bpf_session_cookie(). The verifier inline handles bpf_session_is_return()
for fsession, but what happens when an fsession program calls
bpf_session_cookie()?
Looking at bpf_session_cookie() in the same file:
__bpf_kfunc __u64 *bpf_session_cookie(void *ctx)
{
struct bpf_session_run_ctx *session_ctx;
session_ctx = container_of(current->bpf_ctx, struct bpf_session_run_ctx, run_ctx);
return session_ctx->data;
}
This assumes current->bpf_ctx points to a struct bpf_session_run_ctx, but
fsession programs use struct bpf_tramp_run_ctx (set up in __bpf_prog_enter*).
The container_of() will return an incorrect pointer, and session_ctx->data
will read from the wrong memory location (the saved_run_ctx field of
bpf_tramp_run_ctx instead of the session cookie).
Is this intentional to defer bpf_session_cookie() support to a later commit?
If so, should the filter perhaps only allow bpf_session_is_return() for
fsession at this point?
Note: I see that commit b8f4610f8738 ("bpf: support fsession for
bpf_session_cookie") in the same series adds the verifier inline for
bpf_session_cookie() with fsession, which would resolve this. However, at
this commit, calling bpf_session_cookie() from an fsession program would
produce incorrect results.
return 0; }
[ ... ]
+static int __init bpf_trace_kfuncs_init(void)
{
- return register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_kprobe_multi_kfunc_set);
+ int err = 0;
+
+ err = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_session_kfunc_set);
+ err = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_session_kfunc_set);
+
+ return err;
}--- 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/21308666922