linux-kernel - [PATCH 4.19 003/131] bpftool: Fix printing incorrect pointer in btf_dump

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Message-Id: <20200428182225.839842521@linuxfoundation.org>
Date:   Tue, 28 Apr 2020 20:23:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Martin KaFai Lau <kafai@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 4.19 003/131] bpftool: Fix printing incorrect pointer in btf_dump_ptr

From: Martin KaFai Lau <kafai@...com>

commit 555089fdfc37ad65e0ee9b42ca40c238ff546f83 upstream.

For plain text output, it incorrectly prints the pointer value
"void *data".  The "void *data" is actually pointing to memory that
contains a bpf-map's value.  The intention is to print the content of
the bpf-map's value instead of printing the pointer pointing to the
bpf-map's value.

In this case, a member of the bpf-map's value is a pointer type.
Thus, it should print the "*(void **)data".

Fixes: 22c349e8db89 ("tools: bpftool: fix format strings and arguments for jsonw_printf()")
Signed-off-by: Martin KaFai Lau <kafai@...com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>
Link: https://lore.kernel.org/bpf/20200110231644.3484151-1-kafai@fb.com
Cc: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 tools/bpf/bpftool/btf_dumper.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/bpf/bpftool/btf_dumper.c
+++ b/tools/bpf/bpftool/btf_dumper.c
@@ -26,7 +26,7 @@ static void btf_dumper_ptr(const void *d
 			   bool is_plain_text)
 {
 	if (is_plain_text)
-		jsonw_printf(jw, "%p", data);
+		jsonw_printf(jw, "%p", *(void **)data);
 	else
 		jsonw_printf(jw, "%lu", *(unsigned long *)data);
 }