linux-kernel - [RFC PATCH v5 07/30] bpf tools: Check endianess and make libbpf fail early

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1433144296-74992-8-git-send-email-wangnan0@huawei.com>
Date:	Mon, 1 Jun 2015 07:37:53 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<namhyung@...nel.org>, <alexei.starovoitov@...il.com>,
	<masami.hiramatsu.pt@...achi.com>, <acme@...nel.org>,
	<paulus@...ba.org>, <a.p.zijlstra@...llo.nl>, <mingo@...hat.com>,
	<jolsa@...nel.org>, <dsahern@...il.com>, <daniel@...earbox.net>,
	<brendan.d.gregg@...il.com>
CC:	<lizefan@...wei.com>, <hekuang@...wei.com>, <xiakaixu@...wei.com>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>
Subject: [RFC PATCH v5 07/30] bpf tools: Check endianess and make libbpf fail early

Check endianess according to EHDR. Code is taken from
tools/perf/util/symbol-elf.c.

Libbpf doesn't magically convert missmatched endianess. See discussion
on https://lkml.org/lkml/2015/5/18/650 that, even if we swap
eBPF instructions to correct byte order, we are unable to deal with
endianess in code logical generated by LLVM.

Therefore, libbpf should simply reject missmatched ELF object, and let
LLVM to create good code.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Acked-by: Alexei Starovoitov <ast@...mgrid.com>
---
 tools/lib/bpf/libbpf.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0824822..5d56c40 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -166,6 +166,34 @@ errout:
 	return err;
 }
 
+static int
+bpf_object__check_endianess(struct bpf_object *obj)
+{
+	static unsigned int const endian = 1;
+
+	switch (obj->efile.ehdr.e_ident[EI_DATA]) {
+	case ELFDATA2LSB:
+		/* We are big endian, BPF obj is little endian. */
+		if (*(unsigned char const *)&endian != 1)
+			goto mismatch;
+		break;
+
+	case ELFDATA2MSB:
+		/* We are little endian, BPF obj is big endian. */
+		if (*(unsigned char const *)&endian != 0)
+			goto mismatch;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+
+mismatch:
+	pr_warning("Error: endianess mismatch.\n");
+	return -EINVAL;
+}
+
 struct bpf_object *bpf_object__open(const char *path)
 {
 	struct bpf_object *obj;
@@ -187,6 +215,8 @@ struct bpf_object *bpf_object__open(const char *path)
 
 	if (bpf_object__elf_init(obj))
 		goto out;
+	if (bpf_object__check_endianess(obj))
+		goto out;
 
 	bpf_object__elf_finish(obj);
 	return obj;
-- 
1.8.3.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/