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From: Yongji Xie <xieyongji@bytedance.com>
To: "Philippe Mathieu-Daudé" <philmd@linaro.org>
Cc: "qemu devel list" <qemu-devel@nongnu.org>,
	"Stefan Hajnoczi" <stefanha@redhat.com>,
	"Bin Meng" <bin.meng@windriver.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	"Markus Armbruster" <armbru@redhat.com>,
	"Kevin Wolf" <kwolf@redhat.com>
Subject: Re: [PATCH-for-7.2 v2] libvduse: Avoid warning about dangerous use of strncpy()
Date: Sat, 12 Nov 2022 15:53:22 +0800	[thread overview]
Message-ID: <CACycT3s=6uYv2fotr46afh+WE+7N1NcDsRKpURV2RCbKuUoqcw@mail.gmail.com> (raw)
In-Reply-To: <20221111124550.35753-1-philmd@linaro.org>

On Fri, Nov 11, 2022 at 8:45 PM Philippe Mathieu-Daudé
<philmd@linaro.org> wrote:
>
> From: Philippe Mathieu-Daudé <f4bug@amsat.org>
>
> GCC 8 added a -Wstringop-truncation warning:
>
>   The -Wstringop-truncation warning added in GCC 8.0 via r254630 for
>   bug 81117 is specifically intended to highlight likely unintended
>   uses of the strncpy function that truncate the terminating NUL
>   character from the source string.
>
> Here the next line indeed unconditionally zeroes the last byte, but
> 1/ the buffer has been calloc'd, so we don't need to add an extra
> byte, and 2/ we called vduse_name_is_invalid() which checked the
> string length, so we can simply call strcpy().
>
> This fixes when using gcc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0:
>
>   [42/666] Compiling C object subprojects/libvduse/libvduse.a.p/libvduse.c.o
>   FAILED: subprojects/libvduse/libvduse.a.p/libvduse.c.o
>   cc -m64 -mcx16 -Isubprojects/libvduse/libvduse.a.p -Isubprojects/libvduse -I../../subprojects/libvduse [...] -o subprojects/libvduse/libvduse.a.p/libvduse.c.o -c ../../subprojects/libvduse/libvduse.c
>   In file included from /usr/include/string.h:495,
>                    from ../../subprojects/libvduse/libvduse.c:24:
>   In function ‘strncpy’,
>       inlined from ‘vduse_dev_create’ at ../../subprojects/libvduse/libvduse.c:1312:5:
>   /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound 256 equals destination size [-Werror=stringop-truncation]
>     106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
>         |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   cc1: all warnings being treated as errors
>   ninja: build stopped: cannot make progress due to previous errors.
>
> Fixes: d9cf16c0be ("libvduse: Replace strcpy() with strncpy()")
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> Supersedes: <20220919192306.52729-1-f4bug@amsat.org>
> Cc: Xie Yongji <xieyongji@bytedance.com>
> Cc: Kevin Wolf <kwolf@redhat.com>
> ---
>  subprojects/libvduse/libvduse.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>

Reviewed-by: Xie Yongji <xieyongji@bytedance.com>


  parent reply	other threads:[~2022-11-12  7:54 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-11 12:45 [PATCH-for-7.2 v2] libvduse: Avoid warning about dangerous use of strncpy() Philippe Mathieu-Daudé
2022-11-11 15:00 ` Bin Meng
2022-11-11 16:50 ` Stefan Hajnoczi
2022-11-12  7:53 ` Yongji Xie [this message]
2022-11-13 11:31 ` Stefan Hajnoczi

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