glibc/libio/iofwrite.c
Eric Biggers 3d110c7c6e Fix fwrite() reading beyond end of buffer in error path
Partially revert commits 2b766585f9 and
de2fd463b1, which were intended to fix BZ#11741
but caused another, likely worse bug, namely that fwrite() and fputs() could,
in an error path, read data beyond the end of the specified buffer, and
potentially even write this data to the file.

Fix BZ#11741 properly by checking the return value from _IO_padn() in
stdio-common/vfprintf.c.
2013-10-11 22:29:38 +05:30

65 lines
2.3 KiB
C

/* Copyright (C) 1993-2013 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
<http://www.gnu.org/licenses/>.
As a special exception, if you link the code in this file with
files compiled with a GNU compiler to produce an executable,
that does not cause the resulting executable to be covered by
the GNU Lesser General Public License. This exception does not
however invalidate any other reasons why the executable file
might be covered by the GNU Lesser General Public License.
This exception applies to code released by its copyright holders
in files containing the exception. */
#include "libioP.h"
_IO_size_t
_IO_fwrite (buf, size, count, fp)
const void *buf;
_IO_size_t size;
_IO_size_t count;
_IO_FILE *fp;
{
_IO_size_t request = size * count;
_IO_size_t written = 0;
CHECK_FILE (fp, 0);
if (request == 0)
return 0;
_IO_acquire_lock (fp);
if (_IO_vtable_offset (fp) != 0 || _IO_fwide (fp, -1) == -1)
written = _IO_sputn (fp, (const char *) buf, request);
_IO_release_lock (fp);
/* We have written all of the input in case the return value indicates
this or EOF is returned. The latter is a special case where we
simply did not manage to flush the buffer. But the data is in the
buffer and therefore written as far as fwrite is concerned. */
if (written == request || written == EOF)
return count;
else
return written / size;
}
libc_hidden_def (_IO_fwrite)
#ifdef weak_alias
# include <stdio.h>
weak_alias (_IO_fwrite, fwrite)
libc_hidden_weak (fwrite)
# ifndef _IO_MTSAFE_IO
weak_alias (_IO_fwrite, fwrite_unlocked)
libc_hidden_weak (fwrite_unlocked)
# endif
#endif