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    Subject[PATCH 5.5 207/399] tools lib api fs: Fix gcc9 stringop-truncation compilation error
    Date
    From: Andrey Zhizhikin <andrey.z@gmail.com>

    [ Upstream commit 6794200fa3c9c3e6759dae099145f23e4310f4f7 ]

    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@leica-geosystems.com>
    Reviewed-by: Petr Mladek <pmladek@suse.com>
    Acked-by: Jiri Olsa <jolsa@kernel.org>
    Cc: Alexei Starovoitov <ast@kernel.org>
    Cc: Andrii Nakryiko <andriin@fb.com>
    Cc: Daniel Borkmann <daniel@iogearbox.net>
    Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
    Cc: Martin KaFai Lau <kafai@fb.com>
    Cc: Petr Mladek <pmladek@suse.com>
    Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Cc: Song Liu <songliubraving@fb.com>
    Cc: Yonghong Song <yhs@fb.com>
    Cc: bpf@vger.kernel.org
    Cc: netdev@vger.kernel.org
    Link: http://lore.kernel.org/lkml/20191211080109.18765-1-andrey.zhizhikin@leica-geosystems.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 11b3885e833ed..027b18f7ed8cf 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;
    }

    --
    2.20.1


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