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980cb5180e
addgetnetgrentX has a buffer which is grown as per the needs of the requested size either by using alloca or by falling back to malloc if the size is larger than 1K. There are two problems with the alloca bits: firstly, it doesn't really extend the buffer since it does not use the return value of the extend_alloca macro, which is the location of the reallocated buffer. Due to this the buffer does not actually extend itself and hence a subsequent write may overwrite stuff on the stack. The second problem is more subtle - the buffer growth on the stack is discontinuous due to block scope local variables. Combine that with the fact that unlike realloc, extend_alloca does not copy over old content and you have a situation where the buffer just has garbage in the space where it should have had data. This could have been fixed by adding code to copy over old data whenever we call extend_alloca, but it seems unnecessarily complicated. This code is not exactly a performance hotspot (it's called when there is a cache miss, so factors like network lookup or file reads will dominate over memory allocation/reallocation), so this premature optimization is unnecessary. Thanks Brad Hubbard <bhubbard@redhat.com> for his help with debugging the problem. |
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| WUR-REPORT | ||
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. The current GNU/Hurd support requires out-of-tree patches that will eventually be incorporated into an official GNU C Library release. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 2.6.16 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: i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu The code for other CPU configurations supported by volunteers outside of the core glibc maintenance effort is contained in the `ports' add-on, located in the `ports' subdirectory of the source tree. aarch64*-*-linux-gnu alpha*-*-linux-gnu am33*-*-linux-gnu Not currently functional arm-*-linux-gnueabi hppa-*-linux-gnu Not currently functional without patches. ia64-*-linux-gnu m68k-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu tilegx-*-linux-gnu tilepro-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see http://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 http://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 http://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., 2000-2013, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.