glibc/gmon/tst-mcleanup.c

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gmon: fix memory corruption issues [BZ# 30101] V2 of this patch fixes an issue in V1, where the state was changed to ON not OFF at end of _mcleanup. I hadn't noticed that (counterintuitively) ON=0 and OFF=3, hence zeroing the buffer turned it back on. So set the state to OFF after the memset. 1. Prevent double free, and reads from unallocated memory, when _mcleanup is (incorrectly) called two or more times in a row, without an intervening call to __monstartup; with this patch, the second and subsequent calls effectively become no-ops instead. While setting tos=NULL is minimal fix, safest action is to zero the whole gmonparam buffer. 2. Prevent memory leak when __monstartup is (incorrectly) called two or more times in a row, without an intervening call to _mcleanup; with this patch, the second and subsequent calls effectively become no-ops instead. 3. After _mcleanup, treat __moncontrol(1) as __moncontrol(0) instead. With zeroing of gmonparam buffer in _mcleanup, this stops the state incorrectly being changed to GMON_PROF_ON despite profiling actually being off. If we'd just done the minimal fix to _mcleanup of setting tos=NULL, there is risk of far worse memory corruption: kcount would point to deallocated memory, and the __profil syscall would make the kernel write profiling data into that memory, which could have since been reallocated to something unrelated. 4. Ensure __moncontrol(0) still turns off profiling even in error state. Otherwise, if mcount overflows and sets state to GMON_PROF_ERROR, when _mcleanup calls __moncontrol(0), the __profil syscall to disable profiling will not be invoked. _mcleanup will free the buffer, but the kernel will still be writing profiling data into it, potentially corrupted arbitrary memory. Also adds a test case for (1). Issues (2)-(4) are not feasible to test. Signed-off-by: Simon Kissane <skissane@gmail.com> Reviewed-by: DJ Delorie <dj@redhat.com>
2023-02-10 21:58:02 +00:00
/* Test program for repeated invocation of _mcleanup
Copyright The GNU Toolchain Authors.
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/>. */
/* Intentionally calls _mcleanup() twice: once manually, it will be
called again as an atexit handler. This is incorrect use of the API,
but the point of the test is to make sure we don't crash when the
API is misused in this way. */
#include <sys/gmon.h>
int
main (void)
{
_mcleanup();
return 0;
}