From f6d4def4e27b13fab174e948b94cd10550d3e10e Mon Sep 17 00:00:00 2001 From: Jonathan Nieder Date: Tue, 27 Sep 2011 18:19:06 -0500 Subject: [BUILTIN] Fix "test -x" as root on FreeBSD 8 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit POSIX.1-2008 ยง4.4 "File Access Permission" sayeth: If execute permission is requested, access shall be granted if execute permission is granted to at least one user by the file permission bits or by an alternate access control mechanism; otherwise, access shall be denied. For historical reasons, POSIX unfortunately also allows access() and faccessat() to return success for X_OK if the current process is privileged, even when the above condition is not fulfilled and actual execution would fail. On the affected platforms, "test -x " as root started returning true on nonexecutable files when dash switched from its own emulation to the true faccessat in v0.5.7~54 (2010-04-02). Work around this by checking the permissions bits when mode == X_OK and geteuid() == 0 on such platforms. Unfortunately the behavior seems to vary from one kernel version to another, so we cannot just check the behavior at compile time and rely on that. A survey of some affected kernels: - NetBSD's kernel moved to the sane semantics in 1997 - OpenBSD's kernel made the same change in version 4.4, three years ago - FreeBSD 9's kernel fixes this but hasn't been released yet It seems safe to only apply the workaround on systems using the FreeBSD kernel for now, and to push for standardization on the expected access()/faccessat() semantics so we can drop the workaround altogether in a few years. To try it on other platforms, use "./configure --enable-test-workaround". Reported-by: Christoph Egger Analysis-by: Petr Salinger Signed-off-by: Jonathan Nieder Signed-off-by: Herbert Xu --- configure.ac | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'configure.ac') diff --git a/configure.ac b/configure.ac index 60a2a26..8ae0dc6 100644 --- a/configure.ac +++ b/configure.ac @@ -90,6 +90,37 @@ AC_CHECK_FUNCS(bsearch faccessat getpwnam getrlimit isalpha killpg \ sigsetmask stpcpy strchrnul strsignal strtod strtoimax \ strtoumax sysconf) +dnl Check whether it's worth working around FreeBSD PR kern/125009. +dnl The traditional behavior of access/faccessat is crazy, but +dnl POSIX.1-2008 explicitly allows those functions to misbehave. +dnl +dnl Unaffected kernels: +dnl +dnl - all versions of Linux +dnl - NetBSD sys/kern/vfs_subr.c 1.64, 1997-04-23 +dnl - FreeBSD 9 (r212002), 2010-09-10 +dnl - OpenBSD sys/kern/vfs_subr.c 1.166, 2008-06-09 +dnl +dnl Also worked around in Debian's libc0.1 2.13-19 when using +dnl kFreeBSD 8. + +AC_ARG_ENABLE(test-workaround, AS_HELP_STRING(--enable-test-workaround, \ + [Guard against faccessat(2) that tells root all files are executable]),, + [enable_test_workaround=auto]) + +if test "enable_test_workaround" = "auto" && + test "$ac_cv_func_faccessat" = yes; then + case `uname -s 2>/dev/null` in + GNU/kFreeBSD | \ + FreeBSD) + enable_test_workaround=yes + esac +fi +if test "$enable_test_workaround" = "yes"; then + AC_DEFINE([HAVE_TRADITIONAL_FACCESSAT], [1], + [Define if your faccessat tells root all files are executable]) +fi + if test "$enable_fnmatch" = yes; then use_fnmatch= AC_CHECK_FUNCS(fnmatch, use_fnmatch=yes) -- cgit 1.4.1