linux-kernel - [PATCH 08/20] tools lib api fs: Fix gcc9 stringop-truncation compilation error

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Message-Id: <20200106160705.10899-9-acme@kernel.org>
Date:   Mon,  6 Jan 2020 13:06:53 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Andrey Zhizhikin <andrey.z@...il.com>,
        Andrey Zhizhikin <andrey.zhizhikin@...ca-geosystems.com>,
        Petr Mladek <pmladek@...e.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andriin@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Martin KaFai Lau <kafai@...com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 08/20] tools lib api fs: Fix gcc9 stringop-truncation compilation error

From: Andrey Zhizhikin <andrey.z@...il.com>

GCC9 introduced string hardening mechanisms, which exhibits the error
during fs api compilation:

error: '__builtin_strncpy' specified bound 4096 equals destination size
[-Werror=stringop-truncation]

This comes when the length of copy passed to strncpy is is equal to
destination size, which could potentially lead to buffer overflow.

There is a need to mitigate this potential issue by limiting the size of
destination by 1 and explicitly terminate the destination with NULL.

Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin@...ca-geosystems.com>
Reviewed-by: Petr Mladek <pmladek@...e.com>
Acked-by: Jiri Olsa <jolsa@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andriin@...com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Kefeng Wang <wangkefeng.wang@...wei.com>
Cc: Martin KaFai Lau <kafai@...com>
Cc: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc: Song Liu <songliubraving@...com>
Cc: Yonghong Song <yhs@...com>
Cc: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org
Link: http://lore.kernel.org/lkml/20191211080109.18765-1-andrey.zhizhikin@leica-geosystems.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/lib/api/fs/fs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 11b3885e833e..027b18f7ed8c 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -210,6 +210,7 @@ static bool fs__env_override(struct fs *fs)
 	size_t name_len = strlen(fs->name);
 	/* name + "_PATH" + '\0' */
 	char upper_name[name_len + 5 + 1];
+
 	memcpy(upper_name, fs->name, name_len);
 	mem_toupper(upper_name, name_len);
 	strcpy(&upper_name[name_len], "_PATH");
@@ -219,7 +220,8 @@ static bool fs__env_override(struct fs *fs)
 		return false;
 
 	fs->found = true;
-	strncpy(fs->path, override_path, sizeof(fs->path));
+	strncpy(fs->path, override_path, sizeof(fs->path) - 1);
+	fs->path[sizeof(fs->path) - 1] = '\0';
 	return true;
 }
 
-- 
2.21.1