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From: Adhemerval Zanella <azanella@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] libio: Ensure output buffer for wchars (bug #28828) Date: Tue, 8 Mar 2022 17:26:14 +0000 (GMT) [thread overview] Message-ID: <20220308172614.5BEE03858D35@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=edc696a73a7cb07b1aa68792a845a98d036ee7eb commit edc696a73a7cb07b1aa68792a845a98d036ee7eb Author: José Bollo <jobol@nonadev.net> Date: Tue Mar 8 09:58:16 2022 +0100 libio: Ensure output buffer for wchars (bug #28828) The _IO_wfile_overflow does not check if the write pointer for wide data is valid before access, different than _IO_file_overflow. This leads to crash 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 "fgetwc(stdin);" is necessary since it triggers the bug by setting the flag _IO_CURRENTLY_PUTTING on stdout indirectly (file wfileops.c, function _IO_wfile_underflow, line 213). Signed-off-by: Jose Bollo <jobol@nonadev.net> Diff: --- libio/Makefile | 2 +- libio/tst-bz28828.c | 32 ++++++++++++++++++++++++++++++++ libio/tst-bz28828.input | 1 + libio/wfileops.c | 3 ++- 4 files changed, 36 insertions(+), 2 deletions(-) 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..638a6e2f13 --- /dev/null +++ b/libio/tst-bz28828.c @@ -0,0 +1,32 @@ +/* Unit test for BZ#28828. + Copyright (C) 2022 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <support/xstdio.h> +#include <support/check.h> +#include <wchar.h> + +static int +do_test (void) +{ + setvbuf (stdout, NULL, _IOLBF, 0); + fgetwc (stdin); + fputwc (10, stdout); /* It should not crash here. */ + return 0; +} + +#include <support/test-driver.c> diff --git a/libio/tst-bz28828.input b/libio/tst-bz28828.input new file mode 100644 index 0000000000..ce01362503 --- /dev/null +++ b/libio/tst-bz28828.input @@ -0,0 +1 @@ +hello diff --git a/libio/wfileops.c b/libio/wfileops.c index fb9d45b677..b59a98881f 100644 --- a/libio/wfileops.c +++ b/libio/wfileops.c @@ -412,7 +412,8 @@ _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) { /* Allocate a buffer if needed. */ if (f->_wide_data->_IO_write_base == 0)
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