[PATCH] libbpf: fix feature detectors when using token_fd

[PATCH] libbpf: fix feature detectors when using token_fd

[Andrii Nakryiko]

Adjust `union bpf_attr` size passed to kernel in two feature-detecting
functions to take into account prog_token_fd field.

Libbpf is avoiding memset()'ing entire `union bpf_attr` by only using
minimal set of bpf_attr's fields. Two places have been missed when
wiring BPF token support in libbpf's feature detection logic.

Fix them trivially.

Fixes: f3dcee938f48 ("libbpf: Wire up token_fd into feature probing logic")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/bpf.c      | 2 +-
 tools/lib/bpf/features.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 466a29d80124..2a4c71501a17 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -105,7 +105,7 @@ int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts)
  */
 int probe_memcg_account(int token_fd)
 {
-	const size_t attr_sz = offsetofend(union bpf_attr, attach_btf_obj_fd);
+	const size_t attr_sz = offsetofend(union bpf_attr, prog_token_fd);
 	struct bpf_insn insns[] = {
 		BPF_EMIT_CALL(BPF_FUNC_ktime_get_coarse_ns),
 		BPF_EXIT_INSN(),
diff --git a/tools/lib/bpf/features.c b/tools/lib/bpf/features.c
index 4e783cc7fc4b..a336786a22a3 100644
--- a/tools/lib/bpf/features.c
+++ b/tools/lib/bpf/features.c
@@ -22,7 +22,7 @@ int probe_fd(int fd)
 
 static int probe_kern_prog_name(int token_fd)
 {
-	const size_t attr_sz = offsetofend(union bpf_attr, prog_name);
+	const size_t attr_sz = offsetofend(union bpf_attr, prog_token_fd);
 	struct bpf_insn insns[] = {
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
-- 
2.43.0

Re: [PATCH] libbpf: fix feature detectors when using token_fd

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon, 13 May 2024 11:08:03 -0700 you wrote:
> Adjust `union bpf_attr` size passed to kernel in two feature-detecting
> functions to take into account prog_token_fd field.
> 
> Libbpf is avoiding memset()'ing entire `union bpf_attr` by only using
> minimal set of bpf_attr's fields. Two places have been missed when
> wiring BPF token support in libbpf's feature detection logic.
> 
> [...]

Here is the summary with links:
  - libbpf: fix feature detectors when using token_fd
    https://git.kernel.org/bpf/bpf/c/1de27bba6d50

You are awesome, thank you!
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