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* nptl: Fix Race conditions in pthread cancellation [BZ#12683]Adhemerval Zanella10 days1-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current racy approach is to enable asynchronous cancellation before making the syscall and restore the previous cancellation type once the syscall returns, and check if cancellation has happen during the cancellation entrypoint. As described in BZ#12683, this approach shows 2 problems: 1. Cancellation can act after the syscall has returned from the kernel, but before userspace saves the return value. It might result in a resource leak if the syscall allocated a resource or a side effect (partial read/write), and there is no way to program handle it with cancellation handlers. 2. If a signal is handled while the thread is blocked at a cancellable syscall, the entire signal handler runs with asynchronous cancellation enabled. This can lead to issues if the signal handler call functions which are async-signal-safe but not async-cancel-safe. For the cancellation to work correctly, there are 5 points at which the cancellation signal could arrive: [ ... )[ ... )[ syscall ]( ... 1 2 3 4 5 1. Before initial testcancel, e.g. [*... testcancel) 2. Between testcancel and syscall start, e.g. [testcancel...syscall start) 3. While syscall is blocked and no side effects have yet taken place, e.g. [ syscall ] 4. Same as 3 but with side-effects having occurred (e.g. a partial read or write). 5. After syscall end e.g. (syscall end...*] And libc wants to act on cancellation in cases 1, 2, and 3 but not in cases 4 or 5. For the 4 and 5 cases, the cancellation will eventually happen in the next cancellable entrypoint without any further external event. The proposed solution for each case is: 1. Do a conditional branch based on whether the thread has received a cancellation request; 2. It can be caught by the signal handler determining that the saved program counter (from the ucontext_t) is in some address range beginning just before the "testcancel" and ending with the syscall instruction. 3. SIGCANCEL can be caught by the signal handler and determine that the saved program counter (from the ucontext_t) is in the address range beginning just before "testcancel" and ending with the first uninterruptable (via a signal) syscall instruction that enters the kernel. 4. In this case, except for certain syscalls that ALWAYS fail with EINTR even for non-interrupting signals, the kernel will reset the program counter to point at the syscall instruction during signal handling, so that the syscall is restarted when the signal handler returns. So, from the signal handler's standpoint, this looks the same as case 2, and thus it's taken care of. 5. For syscalls with side-effects, the kernel cannot restart the syscall; when it's interrupted by a signal, the kernel must cause the syscall to return with whatever partial result is obtained (e.g. partial read or write). 6. The saved program counter points just after the syscall instruction, so the signal handler won't act on cancellation. This is similar to 4. since the program counter is past the syscall instruction. So The proposed fixes are: 1. Remove the enable_asynccancel/disable_asynccancel function usage in cancellable syscall definition and instead make them call a common symbol that will check if cancellation is enabled (__syscall_cancel at nptl/cancellation.c), call the arch-specific cancellable entry-point (__syscall_cancel_arch), and cancel the thread when required. 2. Provide an arch-specific generic system call wrapper function that contains global markers. These markers will be used in SIGCANCEL signal handler to check if the interruption has been called in a valid syscall and if the syscalls has side-effects. A reference implementation sysdeps/unix/sysv/linux/syscall_cancel.c is provided. However, the markers may not be set on correct expected places depending on how INTERNAL_SYSCALL_NCS is implemented by the architecture. It is expected that all architectures add an arch-specific implementation. 3. Rewrite SIGCANCEL asynchronous handler to check for both canceling type and if current IP from signal handler falls between the global markers and act accordingly. 4. Adjust libc code to replace LIBC_CANCEL_ASYNC/LIBC_CANCEL_RESET to use the appropriate cancelable syscalls. 5. Adjust 'lowlevellock-futex.h' arch-specific implementations to provide cancelable futex calls. Some architectures require specific support on syscall handling: * On i386 the syscall cancel bridge needs to use the old int80 instruction because the optimized vDSO symbol the resulting PC value for an interrupted syscall points to an address outside the expected markers in __syscall_cancel_arch. It has been discussed in LKML [1] on how kernel could help userland to accomplish it, but afaik discussion has stalled. Also, sysenter should not be used directly by libc since its calling convention is set by the kernel depending of the underlying x86 chip (check kernel commit 30bfa7b3488bfb1bb75c9f50a5fcac1832970c60). * mips o32 is the only kABI that requires 7 argument syscall, and to avoid add a requirement on all architectures to support it, mips support is added with extra internal defines. Checked on aarch64-linux-gnu, arm-linux-gnueabihf, powerpc-linux-gnu, powerpc64-linux-gnu, powerpc64le-linux-gnu, i686-linux-gnu, and x86_64-linux-gnu. [1] https://lkml.org/lkml/2016/3/8/1105 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
* Update copyright dates with scripts/update-copyrightsPaul Eggert2024-01-011-1/+1
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* Update copyright dates with scripts/update-copyrightsJoseph Myers2023-01-061-1/+1
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* Update copyright dates with scripts/update-copyrightsPaul Eggert2022-01-011-1/+1
| | | | | | | | | | | | | | | | | | | | | | | I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 7061 files FOO. I then removed trailing white space from math/tgmath.h, support/tst-support-open-dev-null-range.c, and sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following obscure pre-commit check failure diagnostics from Savannah. I don't know why I run into these diagnostics whereas others evidently do not. remote: *** 912-#endif remote: *** 913: remote: *** 914- remote: *** error: lines with trailing whitespace found ... remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
* Update copyright dates with scripts/update-copyrightsPaul Eggert2021-01-021-1/+1
| | | | | | | | | | | | | | | | I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 6694 files FOO. I then removed trailing white space from benchtests/bench-pthread-locks.c and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this diagnostic from Savannah: remote: *** pre-commit check failed ... remote: *** error: lines with trailing whitespace found remote: error: hook declined to update refs/heads/master
* Update copyright dates with scripts/update-copyrights.Joseph Myers2020-01-011-1/+1
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* Prefer https to http for gnu.org and fsf.org URLsPaul Eggert2019-09-071-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Also, change sources.redhat.com to sourceware.org. This patch was automatically generated by running the following shell script, which uses GNU sed, and which avoids modifying files imported from upstream: sed -ri ' s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g ' \ $(find $(git ls-files) -prune -type f \ ! -name '*.po' \ ! -name 'ChangeLog*' \ ! -path COPYING ! -path COPYING.LIB \ ! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \ ! -path manual/texinfo.tex ! -path scripts/config.guess \ ! -path scripts/config.sub ! -path scripts/install-sh \ ! -path scripts/mkinstalldirs ! -path scripts/move-if-change \ ! -path INSTALL ! -path locale/programs/charmap-kw.h \ ! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \ ! '(' -name configure \ -execdir test -f configure.ac -o -f configure.in ';' ')' \ ! '(' -name preconfigure \ -execdir test -f preconfigure.ac ';' ')' \ -print) and then by running 'make dist-prepare' to regenerate files built from the altered files, and then executing the following to cleanup: chmod a+x sysdeps/unix/sysv/linux/riscv/configure # Omit irrelevant whitespace and comment-only changes, # perhaps from a slightly-different Autoconf version. git checkout -f \ sysdeps/csky/configure \ sysdeps/hppa/configure \ sysdeps/riscv/configure \ sysdeps/unix/sysv/linux/csky/configure # Omit changes that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines git checkout -f \ sysdeps/powerpc/powerpc64/ppc-mcount.S \ sysdeps/unix/sysv/linux/s390/s390-64/syscall.S # Omit change that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
* Update copyright dates with scripts/update-copyrights.Joseph Myers2019-01-011-1/+1
| | | | | | | * All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
* Update copyright dates with scripts/update-copyrights.Joseph Myers2018-01-011-1/+1
| | | | | | | * All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
* Update copyright dates with scripts/update-copyrights.Joseph Myers2017-01-011-1/+1
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* Update copyright dates with scripts/update-copyrights.Joseph Myers2016-01-041-1/+1
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* Update copyright dates with scripts/update-copyrights.Joseph Myers2015-01-021-1/+1
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* Update copyright notices with scripts/update-copyrightsAllan McRae2014-01-011-1/+1
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* Update copyright notices with scripts/update-copyrights.Joseph Myers2013-01-021-1/+1
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* Get rid of ASM_TYPE_DIRECTIVE{,_PREFIX}.Marek Polacek2012-08-021-4/+2
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* Get rid of ASM_GLOBAL_DIRECTIVE.Marek Polacek2012-07-101-1/+1
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* Replace FSF snail mail address with URLs.Paul Eggert2012-02-091-3/+2
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* More fallout from supporting only ELFUlrich Drepper2012-01-081-2/+0
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* Remove non-ELF supportUlrich Drepper2012-01-071-12/+1
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* * sysdeps/sh/sysdep.h: Add cfi instrumentation to asm fragments.Ulrich Drepper2005-12-301-2/+9
| | | | | | | | | | | | | | | | * sysdeps/unix/sysv/linux/sh/sysdep.h: Likewise. * sysdeps/sh/_mcount.S: Add cfi instrumentation. * sysdeps/unix/sh/sysdep.S: Likewise. * sysdeps/unix/sysv/linux/sh/makecontext.S: Adjust cfi_startproc. * sysdeps/unix/sysv/linux/sh/sh4/getcontext.S: Remove now duplicate cfi_startproc and cfi_endproc. * sysdeps/unix/sysv/linux/sh/sh4/setcontext.S: Likewise. * sysdeps/unix/sysv/linux/sh/sh4/swapcontext.S: Likewise. * sysdeps/unix/sysv/linux/sh/sh3/getcontext.S: Likewise. * sysdeps/unix/sysv/linux/sh/sh3/setcontext.S: Likewise. * sysdeps/unix/sysv/linux/sh/sh3/swapcontext.S: Likewise. * sysdeps/unix/sysv/linux/sh/socket.S: Likewise. * sysdeps/unix/sysv/linux/sh/sysdep.S: Add cfi_endproc.
* (CFLAGS-tst-align.c): Add -mpreferred-stack-boundary=4.Ulrich Drepper2004-12-221-9/+2
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* 2.5-18.1Jakub Jelinek2007-07-121-2/+9
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* Update.Ulrich Drepper2001-12-121-1/+9
| | | | | | | | | 2001-12-12 NIIBE Yutaka <gniibe@m17n.org> * sysdeps/sh/Makefile: New file. * sysdeps/sh/_mcount.S: New file. * sysdeps/sh/sysdep.h (CALL_MCOUNT): Implemented. * sysdeps/sh/machine-gmon.h: Remove "NOTYET" comment, as we are ready.
* Update to LGPL v2.1.Andreas Jaeger2001-07-061-8/+8
| | | | | | | | | | | | | | 2001-07-06 Paul Eggert <eggert@twinsun.com> * manual/argp.texi: Remove ignored LGPL copyright notice; it's not appropriate for documentation anyway. * manual/libc-texinfo.sh: "Library General Public License" -> "Lesser General Public License". 2001-07-06 Andreas Jaeger <aj@suse.de> * All files under GPL/LGPL version 2: Place under LGPL version 2.1.
* Update.Ulrich Drepper2000-06-121-0/+76
2000-06-12 Kazumoto Kojima <kkojima@rr.iij4u.or.jp> Yutaka Niibe <gniibe@chroot.org> * sysdeps/sh/Dist: New file. * sysdeps/sh/Implies: New file. * sysdeps/sh/gmp-mparam.h: New file. * sysdeps/sh/init-first.c: New file. * sysdeps/sh/machine-gmon.h: New file. * sysdeps/sh/memcpy.S: New file. * sysdeps/sh/memprof.h: New file. * sysdeps/sh/memset.S: New file. * sysdeps/sh/sh3/__longjmp.S: New file. * sysdeps/sh/sh3/bits/endian.h: New file. * sysdeps/sh/sh3/bits/huge_val.h: New file. * sysdeps/sh/sh3/bits/setjmp.h: New file. * sysdeps/sh/sh3/bsd-_setjmp.S: New file. * sysdeps/sh/sh3/bsd-setjmp.S: New file. * sysdeps/sh/sh3/dl-machine.h: New file. * sysdeps/sh/sh3/elf/initfini.c: New file. * sysdeps/sh/sh3/elf/start.S: New file. * sysdeps/sh/sh3/setjmp.S: New file. * sysdeps/sh/sh3/sys/ucontext.h: New file. * sysdeps/sh/sh4/__longjmp.S: New file. * sysdeps/sh/sh4/bits/endian.h: New file. * sysdeps/sh/sh4/bits/huge_val.h: New file. * sysdeps/sh/sh4/bits/setjmp.h: New file. * sysdeps/sh/sh4/bsd-_setjmp.S: New file. * sysdeps/sh/sh4/bsd-setjmp.S: New file. * sysdeps/sh/sh4/dl-machine.h: New file. * sysdeps/sh/sh4/elf/initfini.c: New file. * sysdeps/sh/sh4/elf/start.S: New file. * sysdeps/sh/sh4/fpu/bits/fenv.h: New file. * sysdeps/sh/sh4/fpu/bits/huge_val.h: New file. * sysdeps/sh/sh4/fpu/bits/mathdef.h: New file. * sysdeps/sh/sh4/fpu/fclrexcpt.c: New file. * sysdeps/sh/sh4/fpu/fegetenv.c: New file. * sysdeps/sh/sh4/fpu/fegetround.c: New file. * sysdeps/sh/sh4/fpu/feholdexcpt.c: New file. * sysdeps/sh/sh4/fpu/fesetenv.c: New file. * sysdeps/sh/sh4/fpu/fesetround.c: New file. * sysdeps/sh/sh4/fpu/fpu_control.h: New file. * sysdeps/sh/sh4/fpu/fraiseexcpt.c: New file. * sysdeps/sh/sh4/fpu/fsetexcptflg.c: New file. * sysdeps/sh/sh4/fpu/ftestexcept.c: New file. * sysdeps/sh/sh4/fpu/libm-test-ulps: New file. * sysdeps/sh/sh4/setjmp.S: New file. * sysdeps/sh/sh4/sys/ucontext.h: New file. * sysdeps/sh/strlen.S: New file. * sysdeps/sh/sysdep.h: New file. * sysdeps/unix/sh/sysdep.S: New file. * sysdeps/unix/sh/sysdep.h: New file. * sysdeps/unix/sysv/linux/sh/Dist: New file. * sysdeps/unix/sysv/linux/sh/Makefile: New file. * sysdeps/unix/sysv/linux/sh/Versions: New file. * sysdeps/unix/sysv/linux/sh/bits/mman.h: New file. * sysdeps/unix/sysv/linux/sh/bits/resource.h: New file. * sysdeps/unix/sysv/linux/sh/brk.c: New file. * sysdeps/unix/sysv/linux/sh/chown.c: New file. * sysdeps/unix/sysv/linux/sh/clone.S: New file. * sysdeps/unix/sysv/linux/sh/fchown.c: New file. * sysdeps/unix/sysv/linux/sh/fxstat.c: New file. * sysdeps/unix/sysv/linux/sh/getegid.c: New file. * sysdeps/unix/sysv/linux/sh/geteuid.c: New file. * sysdeps/unix/sysv/linux/sh/getgroups.c: New file. * sysdeps/unix/sysv/linux/sh/getresgid.c: New file. * sysdeps/unix/sysv/linux/sh/getresuid.c: New file. * sysdeps/unix/sysv/linux/sh/getrlimit.c: New file. * sysdeps/unix/sysv/linux/sh/getrlimit64.c: New file. * sysdeps/unix/sysv/linux/sh/getuid.c: New file. * sysdeps/unix/sysv/linux/sh/lchown.c: New file. * sysdeps/unix/sysv/linux/sh/lxstat.c: New file. * sysdeps/unix/sysv/linux/sh/msgctl.c: New file. * sysdeps/unix/sysv/linux/sh/oldgetrlimit64.c: New file. * sysdeps/unix/sysv/linux/sh/pipe.S: New file. * sysdeps/unix/sysv/linux/sh/profil-counter.h: New file. * sysdeps/unix/sysv/linux/sh/semctl.c: New file. * sysdeps/unix/sysv/linux/sh/setegid.c: New file. * sysdeps/unix/sysv/linux/sh/seteuid.c: New file. * sysdeps/unix/sysv/linux/sh/setfsgid.c: New file. * sysdeps/unix/sysv/linux/sh/setfsuid.c: New file. * sysdeps/unix/sysv/linux/sh/setgid.c: New file. * sysdeps/unix/sysv/linux/sh/setgroups.c: New file. * sysdeps/unix/sysv/linux/sh/setregid.c: New file. * sysdeps/unix/sysv/linux/sh/setresgid.c: New file. * sysdeps/unix/sysv/linux/sh/setresuid.c: New file. * sysdeps/unix/sysv/linux/sh/setreuid.c: New file. * sysdeps/unix/sysv/linux/sh/setrlimit.c: New file. * sysdeps/unix/sysv/linux/sh/setuid.c: New file. * sysdeps/unix/sysv/linux/sh/sh3/register-dump.h: New file. * sysdeps/unix/sysv/linux/sh/sh4/register-dump.h: New file. * sysdeps/unix/sysv/linux/sh/shmctl.c: New file. * sysdeps/unix/sysv/linux/sh/sigcontextinfo.h: New file. * sysdeps/unix/sysv/linux/sh/socket.S: New file. * sysdeps/unix/sysv/linux/sh/sys/io.h: New file. * sysdeps/unix/sysv/linux/sh/sys/ucontext.h: New file. * sysdeps/unix/sysv/linux/sh/sys/user.h: New file. * sysdeps/unix/sysv/linux/sh/syscalls.list: New file. * sysdeps/unix/sysv/linux/sh/sysdep.S: New file. * sysdeps/unix/sysv/linux/sh/sysdep.h: New file. * sysdeps/unix/sysv/linux/sh/vfork.S: New file. * sysdeps/unix/sysv/linux/sh/xstat.c: New file.
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