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bde1218720
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> |
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This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arc*-*-linux-gnu arm-*-linux-gnueabi csky-*-linux-gnuabiv2 hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu loongarch64-*-linux-gnu Hardware floating point, LE only. m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu or1k-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv32-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see https://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at https://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see https://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.