All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Jiri Olsa <jolsa@redhat.com>,
	Eelco Chaudron <echaudro@redhat.com>,
	KP Singh <kpsingh@chromium.org>,
	netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH bpf-next v9 06/11] bpf: Fix context type resolving for extension programs
Date: Fri, 25 Sep 2020 23:25:05 +0200	[thread overview]
Message-ID: <160106910591.27725.1499697900366462609.stgit@toke.dk> (raw)
In-Reply-To: <160106909952.27725.8383447127582216829.stgit@toke.dk>

From: Toke Høiland-Jørgensen <toke@redhat.com>

Eelco reported we can't properly access arguments if the tracing
program is attached to extension program.

Having following program:

  SEC("classifier/test_pkt_md_access")
  int test_pkt_md_access(struct __sk_buff *skb)

with its extension:

  SEC("freplace/test_pkt_md_access")
  int test_pkt_md_access_new(struct __sk_buff *skb)

and tracing that extension with:

  SEC("fentry/test_pkt_md_access_new")
  int BPF_PROG(fentry, struct sk_buff *skb)

It's not possible to access skb argument in the fentry program,
with following error from verifier:

  ; int BPF_PROG(fentry, struct sk_buff *skb)
  0: (79) r1 = *(u64 *)(r1 +0)
  invalid bpf_context access off=0 size=8

The problem is that btf_ctx_access gets the context type for the
traced program, which is in this case the extension.

But when we trace extension program, we want to get the context
type of the program that the extension is attached to, so we can
access the argument properly in the trace program.

This version of the patch is tweaked slightly from Jiri's original one,
since the refactoring in the previous patches means we have to get the
target prog type from the new variable in prog->aux instead of directly
from the target prog.

Reported-by: Eelco Chaudron <echaudro@redhat.com>
Suggested-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 kernel/bpf/btf.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index faf57c6f8804..7fd4757a573d 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3860,7 +3860,14 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 
 	info->reg_type = PTR_TO_BTF_ID;
 	if (dst_prog) {
-		ret = btf_translate_to_vmlinux(log, btf, t, dst_prog->type, arg);
+		enum bpf_prog_type dst_type;
+
+		if (dst_prog->type == BPF_PROG_TYPE_EXT)
+			dst_type = dst_prog->aux->saved_dst_prog_type;
+		else
+			dst_type = dst_prog->type;
+
+		ret = btf_translate_to_vmlinux(log, btf, t, dst_type, arg);
 		if (ret > 0) {
 			info->btf_id = ret;
 			return true;


  parent reply	other threads:[~2020-09-25 21:25 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-25 21:24 [PATCH bpf-next v9 00/11] bpf: Support multi-attach for freplace programs Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 01/11] bpf: disallow attaching modify_return tracing functions to other BPF programs Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 02/11] bpf: change logging calls from verbose() to bpf_log() and use log pointer Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 03/11] bpf: verifier: refactor check_attach_btf_id() Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 04/11] bpf: move prog->aux->linked_prog and trampoline into bpf_link on attach Toke Høiland-Jørgensen
2020-09-29  0:05   ` Alexei Starovoitov
2020-09-29 10:47     ` Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 05/11] bpf: support attaching freplace programs to multiple attach points Toke Høiland-Jørgensen
2020-09-29  7:07   ` Dan Carpenter
2020-09-29  7:07     ` Dan Carpenter
2020-09-25 21:25 ` Toke Høiland-Jørgensen [this message]
2020-09-25 21:25 ` [PATCH bpf-next v9 07/11] libbpf: add support for freplace attachment in bpf_link_create Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 08/11] selftests: add test for multiple attachments of freplace program Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 09/11] selftests/bpf: Adding test for arg dereference in extension trace Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 10/11] selftests: Add selftest for disallowing modify_return attachment to freplace Toke Høiland-Jørgensen
2020-09-25 21:25 ` [PATCH bpf-next v9 11/11] selftests: Remove fmod_ret from test_overhead Toke Høiland-Jørgensen
2020-09-29  0:22   ` Alexei Starovoitov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=160106910591.27725.1499697900366462609.stgit@toke.dk \
    --to=toke@redhat.com \
    --cc=andriin@fb.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=echaudro@redhat.com \
    --cc=john.fastabend@gmail.com \
    --cc=jolsa@redhat.com \
    --cc=kafai@fb.com \
    --cc=kpsingh@chromium.org \
    --cc=netdev@vger.kernel.org \
    --cc=songliubraving@fb.com \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.