https://bugs.freedesktop.org/show_bug.cgi?id=72580
Priority: medium
Bug ID: 72580
CC: lenn...@poettering.net
Assignee: pulseaudio-bugs@lists.freedesktop.org
Summary: pulseaudio's use of sys/capability.h is non-POSIX
QA Contact: pulseaudio-bugs@lists.freedesktop.org
Severity: normal
Classification: Unclassified
OS: All
Reporter: de...@desrt.ca
Hardware: Other
Status: NEW
Version: unspecified
Component: daemon
Product: PulseAudio
The configure script for pulseaudio has this:
CAP_LIBS=''
AC_ARG_WITH([caps],
AS_HELP_STRING([--without-caps],[Omit support for POSIX capabilities.]))
if test "x${with_caps}" != "xno"; then
AC_SEARCH_LIBS([cap_init], [cap], [], [
if test "x${with_caps}" = "xyes" ; then
AC_MSG_ERROR([*** POSIX caps libraries not found])
fi])
AC_CHECK_HEADERS([sys/capability.h], [], [
if test "x${with_caps}" = "xyes" ; then
AC_MSG_ERROR([*** POSIX caps headers not found])
fi])
fi
Then in the daemon's source:
void pa_drop_caps(void) {
#ifdef HAVE_SYS_CAPABILITY_H
cap_t caps;
pa_assert_se(caps = cap_init());
pa_assert_se(cap_clear(caps) == 0);
pa_assert_se(cap_set_proc(caps) == 0);
pa_assert_se(cap_free(caps) == 0);
#else
pa_log_warn("Normally all extra capabilities would be dropped now, but "
"that's impossible because this Pulseaudio was built without "
"libcap support.");
#endif
}
POSIX does not specify what such a file should contain -- the attempt to
standardise it seems to have failed, as evidenced by the comment at the top of
Linux's version of this file:
* defunct POSIX.1e Standard: 25.2 Capabilities
Meanwhile, the combination of the two checks above produces the wrong
behaviour.
Imagine a system where sys/capability.h exists, but not cap_init (FreeBSD is
such a system, for example).
The first check fails due to missing cap_init, but because --with-caps=yes was
not explicitly given, the failure is ignored.
The second check, which is independent of the first check then passes, because
we do find sys/capability.h. This results in HAVE_SYS_CAPABILITY_H being
defined, and then the caps code gets enabled in pa_drop_caps().
Inside the #ifdef for HAVE_SYS_CAPABILITY_H there should probably also be an
#ifdef __linux before using that Linux-style capabilities code. There could
then ideally be another branch for BSD-style sys/capability.h.
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