[Bug nptl/22743] __pthread_register_cancel corrupts stack after f81ddabffd

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https://sourceware.org/bugzilla/show_bug.cgi?id=22743

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2ec0e7eade0ea1258acd5c6f5e5e9bfaeb5041a8

commit 2ec0e7eade0ea1258acd5c6f5e5e9bfaeb5041a8
Author: Carlos O'Donell <carlos@systemhalted.org>
Date:   Wed Jan 24 20:35:22 2018 -0800

    Revert Intel CET changes to __jmp_buf_tag (Bug 22743)

    In commit cba595c350e52194e10c0006732e1991e3d0803b and commit
    f81ddabffd76ac9dd600b02adbf3e1dac4bb10ec, ABI compatibility with
    applications was broken by increasing the size of the on-stack
    allocated __pthread_unwind_buf_t beyond the oringal size.
    Applications only have the origianl space available for
    __pthread_unwind_register, and __pthread_unwind_next to use,
    any increase in the size of __pthread_unwind_buf_t causes these
    functions to write beyond the original structure into other
    on-stack variables leading to segmentation faults in common
    applications like vlc. The only workaround is to version those
    functions which operate on the old sized objects, but this must
    happen in glibc 2.28.

    Thank you to Andrew Senkevich, H.J. Lu, and Aurelien Jarno, for
    submitting reports and tracking the issue down.

    The commit reverts the above mentioned commits and testing on
    x86_64 shows that the ABI compatibility is restored. A tst-cleanup1
    regression test linked with an older glibc now passes when run
    with the newly built glibc. Previously a tst-cleanup1 linked with
    an older glibc would segfault when run with an affected glibc build.

    Tested on x86_64 with no regressions.

    Signed-off-by: Carlos O'Donell <carlos@redhat.com>

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                                          |   30 ++++++++++++++++
 bits/types/__cancel_jmp_buf_tag.h                  |   28 ---------------
 nptl/Makefile                                      |    3 +-
 nptl/descr.h                                       |    3 --
 sysdeps/i386/nptl/tcb-offsets.sym                  |    1 -
 sysdeps/i386/nptl/tls.h                            |    4 --
 sysdeps/nptl/pthread.h                             |    7 +++-
 sysdeps/unix/sysv/linux/hppa/pthread.h             |    7 +++-
 .../linux/x86/bits/types/__cancel_jmp_buf_tag.h    |   31 -----------------
 sysdeps/unix/sysv/linux/x86/nptl/pthreadP.h        |   36 --------------------
 sysdeps/unix/sysv/linux/x86/pthreaddef.h           |   22 ------------
 sysdeps/x86_64/nptl/tcb-offsets.sym                |    1 -
 sysdeps/x86_64/nptl/tls.h                          |    5 +--
 13 files changed, 42 insertions(+), 136 deletions(-)
 delete mode 100644 bits/types/__cancel_jmp_buf_tag.h
 delete mode 100644
sysdeps/unix/sysv/linux/x86/bits/types/__cancel_jmp_buf_tag.h
 delete mode 100644 sysdeps/unix/sysv/linux/x86/nptl/pthreadP.h
 delete mode 100644 sysdeps/unix/sysv/linux/x86/pthreaddef.h

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