[all-commits] [llvm/llvm-project] ad294e: [sanitizers] Fix interception of GLibc regexec

[Alexander Richardson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ad294e572bc5c16f9dc420cc994322de6ca3fbfb
      https://github.com/llvm/llvm-project/commit/ad294e572bc5c16f9dc420cc994322de6ca3fbfb
  Author: Alex Richardson <Alexander.Richardson at cl.cam.ac.uk>
  Date:   2021-03-08 (Mon, 08 Mar 2021)

  Changed paths:
    M compiler-rt/lib/asan/asan_interceptors.cpp
    M compiler-rt/lib/asan/asan_interceptors.h
    M compiler-rt/lib/memprof/memprof_interceptors.cpp
    M compiler-rt/lib/memprof/memprof_interceptors.h
    M compiler-rt/lib/msan/msan_interceptors.cpp
    M compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
    M compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
    A compiler-rt/test/sanitizer_common/TestCases/Posix/regex_startend.cpp

  Log Message:
  -----------
  [sanitizers] Fix interception of GLibc regexec

Previously, on GLibc systems, the interceptor was calling __compat_regexec
(regexec at GLIBC_2.2.5) insead of the newer __regexec (regexec at GLIBC_2.3.4).
The __compat_regexec strips the REG_STARTEND flag but does not report an
error if other flags are present. This can result in infinite loops for
programs that use REG_STARTEND to find all matches inside a buffer (since
ignoring REG_STARTEND means that the search always starts from the first
character).

The underlying issue is that GLibc's dlsym(RTLD_NEXT, ...) appears to
always return the oldest versioned symbol instead of the default. This
means it does not match the behaviour of dlsym(RTLD_DEFAULT, ...) or the
behaviour documented in the manpage.

It appears a similar issue was encountered with realpath and worked around
in 77ef78a0a5dbaa364529bd05ed7a7bd9a71dd8d4.

See also https://sourceware.org/bugzilla/show_bug.cgi?id=14932 and
https://sourceware.org/bugzilla/show_bug.cgi?id=1319.

Fixes https://github.com/google/sanitizers/issues/1371

Reviewed By: #sanitizers, vitalybuka, marxin

Differential Revision: https://reviews.llvm.org/D96348