From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: "José Bollo" <jobol@nonadev.net>, libc-alpha@sourceware.org
Subject: Re: [PATCH] libio: Ensure output buffer for wchars (bug 28828)
Date: Mon, 21 Feb 2022 16:14:55 -0300 [thread overview]
Message-ID: <89639a82-614f-6fb8-2e8c-0d503bab6d6c@linaro.org> (raw)
In-Reply-To: <20220214202352.7784-1-jobol@nonadev.net>
On 14/02/2022 17:23, José Bollo wrote:
> From: "jobol@nonadev.net" <jobol@nonadev.net>
>
> When fileops.c checks for nullity of the write pointer,
> in order to ensure its allocation, before that patch,
> wfileops didn't. This was leading to crashes on some cases,
> as described by bug 28828.
>
> The minimal sequence to produce the crash was:
>
> #include <stdio.h>
> #include <wchar.h>
> int main(int ac, char **av)
> {
> setvbuf(stdout, NULL, _IOLBF, 0);
> fgetwc(stdin);
> fputwc(10, stdout); /*CRASH HERE!*/
> return 0;
> }
>
> The line "fgetwc(stdin);" is necessary. It introduces the
> bug by setting the flag _IO_CURRENTLY_PUTTING of stdout
> indirectly (file wfileops.c, function _IO_wfile_underflow, line 213).
>
> Signed-off-by: Jose Bollo <jobol@nonadev.net>
> ---
> libio/Makefile | 2 +-
> libio/tst-bz28828.c | 10 ++++++++++
> libio/wfileops.c | 5 +++--
> 3 files changed, 14 insertions(+), 3 deletions(-)
> create mode 100644 libio/tst-bz28828.c
>
> diff --git a/libio/Makefile b/libio/Makefile
> index 0e5f348bea..e97387743f 100644
> --- a/libio/Makefile
> +++ b/libio/Makefile
> @@ -66,7 +66,7 @@ tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc \
> tst-fwrite-error tst-ftell-partial-wide tst-ftell-active-handler \
> tst-ftell-append tst-fputws tst-bz22415 tst-fgetc-after-eof \
> tst-sprintf-ub tst-sprintf-chk-ub tst-bz24051 tst-bz24153 \
> - tst-wfile-sync
> + tst-wfile-sync tst-bz28828
>
> tests-internal = tst-vtables tst-vtables-interposed
>
> diff --git a/libio/tst-bz28828.c b/libio/tst-bz28828.c
> new file mode 100644
> index 0000000000..f5849d2ca6
> --- /dev/null
> +++ b/libio/tst-bz28828.c
> @@ -0,0 +1,10 @@
> +#include <stdio.h>
> +#include <wchar.h>
> +int main(int ac, char **av)
> +{
> + setvbuf(stdout, NULL, _IOLBF, 0);
> + fgetwc(stdin);
> + fputwc(10, stdout); /*SHOUDN'T CRASH HERE!*/
> + return 0;
> +}
> +
Sorry but this test is unacceptable, it blocks the make check indefinitely
(triggering a failure) and does not use libsupport. This fix requires a
proper testcase, there multiple ways to do, so please check an already
test on libio.
> diff --git a/libio/wfileops.c b/libio/wfileops.c
> index fb9d45b677..aa94a22983 100644
> --- a/libio/wfileops.c
> +++ b/libio/wfileops.c
> @@ -412,10 +412,11 @@ _IO_wfile_overflow (FILE *f, wint_t wch)
> return WEOF;
> }
> /* If currently reading or no buffer allocated. */
> - if ((f->_flags & _IO_CURRENTLY_PUTTING) == 0)
> + if ((f->_flags & _IO_CURRENTLY_PUTTING) == 0
> + || f->_wide_data->_IO_write_base == NULL)
> {
It seems ok, the _IOFBF buffer type has a specific case for buf being
null where it ended up calling _IO_DOALLOCATE (which _IOLBF does not).
> /* Allocate a buffer if needed. */
> - if (f->_wide_data->_IO_write_base == 0)
> + if (f->_wide_data->_IO_write_base == NULL)
I would prefer to avoid make style change on a bug fix.
> {
> _IO_wdoallocbuf (f);
> _IO_free_wbackup_area (f);
next prev parent reply other threads:[~2022-02-21 19:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 20:23 José Bollo
2022-02-21 19:14 ` Adhemerval Zanella [this message]
-- strict thread matches above, loose matches on Subject: below --
2022-02-22 20:55 [PATCH v3] " jobol
2022-03-08 8:54 ` [PATCH] " jobol
2022-02-13 19:52 jobol
2022-02-14 14:15 ` Adhemerval Zanella
2022-02-14 18:10 ` José Bollo
2022-02-14 18:37 ` Adhemerval Zanella
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