fprintf() crashes on wide-oriented stream.

[Takashi Yano]

Ping?

Is this Corinna's domain?

On Tue, 26 Sep 2023 17:30:13 +0900
Takashi Yano wrote:
> On Tue, 26 Sep 2023 12:41:47 +0900
> Takashi Yano wrote:
> > Hi,
> > 
> > I noticed that the following test case crashes at printf() with current
> > newlib.
> > 
> > 
> > #include <stdio.h>
> > #include <wchar.h>
> > #include <locale.h>
> > 
> > int main()
> > {
> > 	setlocale(LC_ALL, "C.UTF-8");
> > 	wprintf(L"%ls\n", L"aaaa"); /* or fwide(stdout, 1); */
> > 	printf("%ls\n", L"bbbb");  /* <--- crash here */
> > 	return 0;
> > }
> > 
> > 
> > I looked into this problem and found the cause.
> > 
> > A narrow char string which can be odd bytes in length is cast into
> > a wide char string which should be even bytes in length in __sprint_r/
> > __sfputs_r based on the __SWID flag. As a result, if the length is
> > odd bytes, the reading buffer runs over the buffer length, which causes
> > a crash. If the length is even bytes, crash does not happen, but garbage
> > is printed. This hapens if printf("%ls\r\n", L"bbbb"); is used instead.
> >                                       ^^
> > 
> > The same issue seemed to be reported ten years ago.
> > https://sourceware.org/pipermail/newlib/2013/010831.html
> > 
> > I have built a patch attached for this issue.
> > 
> > With this patch, __sfputs_r/__sprint_r is split into two versions, one
> > is for vfprintf which does not handle wide string, and the other (newly
> > introduced __sfputws_r/__swprin_r) is for vfwprintf which handles wide
> > string. Please note that fprintf gets working for wide orient stream
> > just like BSD libc, which behaves differently from GNU libc.
> > 
> > This patch also fixes nano-vfprintf.c as well as vfprintf.c/vfwprintf.c
> > in the same manner.
> 
> v2: Remove __sprint_r from nano-vfprintf.c which does not seem to be used
>     anymore.
> 
> -- 
> Takashi Yano <takashi.yano@nifty.ne.jp>


-- 
Takashi Yano <takashi.yano@nifty.ne.jp>