linux-kernel - [PATCH bpf] bpftool: Fix NULL pointer dereference when pin {PROG, MAP, LINK} without FILE

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Date:   Wed,  2 Nov 2022 16:40:34 +0800
From:   Pu Lehui <pulehui@...weicloud.com>
To:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Quentin Monnet <quentin@...valent.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Pu Lehui <pulehui@...wei.com>,
        Pu Lehui <pulehui@...weicloud.com>
Subject: [PATCH bpf] bpftool: Fix NULL pointer dereference when pin {PROG, MAP, LINK} without FILE

From: Pu Lehui <pulehui@...wei.com>

When using bpftool to pin {PROG, MAP, LINK} without FILE,
segmentation fault will occur. The reson is that the lack
of FILE will cause strlen to trigger NULL pointer dereference.
The corresponding stacktrace is shown below:

do_pin
  do_pin_any
    do_pin_fd
      mount_bpffs_for_pin
        strlen(name) <- NULL pointer dereference

Fix it by adding validation to the common process.

Fixes: 75a1e792c335 ("tools: bpftool: Allow all prog/map handles for pinning objects")
Signed-off-by: Pu Lehui <pulehui@...wei.com>
---
 tools/bpf/bpftool/common.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index e4d33bc8bbbf..653c130a0aaa 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -302,6 +302,9 @@ int do_pin_any(int argc, char **argv, int (*get_fd)(int *, char ***))
 	int err;
 	int fd;
 
+	if (!REQ_ARGS(3))
+		return -EINVAL;
+
 	fd = get_fd(&argc, &argv);
 	if (fd < 0)
 		return fd;
-- 
2.25.1