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SubjectRe: [PATCH v3 3/3] vsprintf: Move space out of string literals in fourcc_string()
On Wed, Jan 26, 2022 at 04:19:17PM +0200, Andy Shevchenko wrote:
> The literals "big-endian" and "little-endian" may be potentially
> occurred in other places. Dropping space allows linker to
> "compress" them by using only a single copy.
>
> Rasmus suggested, while at it, replacing strcpy() + strlen() by
> p = stpcpy(), which is done here as well.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
> v3: no changes
> lib/vsprintf.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 4e8f3e9acb99..e2a1d89f1a5c 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1781,8 +1781,8 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
> *p++ = isascii(c) && isprint(c) ? c : '.';
> }
>
> - strcpy(p, orig & BIT(31) ? " big-endian" : " little-endian");
> - p += strlen(p);
> + *p++ = ' ';
> + p = stpcpy(p, orig & BIT(31) ? "big-endian" : "little-endian");
>
> *p++ = ' ';
> *p++ = '(';

No need for any of the manual construction nor stpcpy():

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index d7ad44f2c8f5..aef8bd2789a9 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1788,14 +1788,9 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
*p++ = isascii(c) && isprint(c) ? c : '.';
}

- strcpy(p, *fourcc & BIT(31) ? " big-endian" : " little-endian");
- p += strlen(p);
-
- *p++ = ' ';
- *p++ = '(';
- p = special_hex_number(p, output + sizeof(output) - 2, *fourcc, sizeof(u32));
- *p++ = ')';
- *p = '\0';
+ snprintf(p, sizeof(output) - sizeof(*fourcc), " %s (0x%x)",
+ *fourcc & BIT(31) ? "big-endian" : " little-endian",
+ *fourcc);

return string(buf, end, output, spec);
}

(untested)

--
Kees Cook

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