Package: dbus
Version: 1.10.8-1
While investigating #823460 "lightdm: SIGPIPE ignored in session" in
developed a libc patch which logs a message whenever any new program
starts up an with unusual setup for SIGPIPE.
The logfile contains entries like this:
2016-04-08 12:15:12 UTC:/sbin/wpa_supplicant[3350] execd oddly
(parent /usr/bin/dbus-daemon[3349]): Broken pipe: SIG_IGN
It is a bug to execute a program with SIGPIPE ignored without its
consent. (Or to put it another way, it is not part of the
specification of programs in general, on a unix system, that they will
function correctly if run with anomalous signal configuration.)
In this case I see quite a few programs in the log being executed with
SIGPIPE set to SIG_IGN. For many of thexe programs I don't really
know whether the consent. But I think I know that wpa_supplicant
doesn't; and I doubt that nm-dispatcher or the various systemd-*
programs document that this is permitted or expected.
In practice the fallout from this bug is likely to be modest because
many of these programs are daemons of one kind or another anyway, and
few of them tend to do their work with a lot of pipes etc.
But one possible consequence is that daemons or other long-lived
service processes might fail to terminate when their socket peer goes
away, and instead might end up spinning on the cpu.
I will attach the glibc patch I used, and an extract from the log it
wrote.
Ian.
-- System Information:
Debian Release: stretch/sid
APT prefers testing
APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 4.5.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.utf-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)
Versions of packages dbus depends on:
ii adduser 3.114
ii init-system-helpers 1.29
ii libapparmor1 2.10-4
ii libaudit1 1:2.4.5-1+b1
ii libc6 2.22-7
ii libcap-ng0 0.7.7-1+b1
ii libdbus-1-3 1.10.8-1
ii libexpat1 2.1.1-1
ii libselinux1 2.5-1
ii libsystemd0 229-5
ii lsb-base 9.20160110
dbus recommends no packages.
Versions of packages dbus suggests:
ii dbus-x11 1.10.8-1
Versions of packages dbus is related to:
ii dbus-x11 1.10.8-1
ii systemd 229-5
pn systemd-sysv <none>
-- no debconf information
diff --git a/csu/init-first.c b/csu/init-first.c
index b3bacdd..751fc5a 100644
--- a/csu/init-first.c
+++ b/csu/init-first.c
@@ -39,6 +39,92 @@ int __libc_argc attribute_hidden;
char **__libc_argv attribute_hidden;
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <time.h>
+
+static void
+__libc_check_sigpipe (const char *argv0)
+{
+ static const int sigs[] = { SIGPIPE, SIGTERM, SIGALRM, 9 };
+ const int *sigp;
+ int sig;
+ struct sigaction sa;
+ sigset_t mask;
+ int r;
+ const char *oddity;
+
+ sig = 0;
+ r = sigprocmask(SIG_UNBLOCK, 0, &mask);
+ if (r) { oddity = strerror(errno); goto bad; }
+
+ for (sigp = sigs; (sig = *sigp); sigp++) {
+ r = sigaction(SIGPIPE, 0, &sa);
+ if (r) { oddity = strerror(errno); goto bad; }
+ if (sa.sa_handler == SIG_IGN) { oddity = "SIG_IGN"; goto bad; }
+ if (sigismember(&mask, sig)) { oddity = "blocked"; goto bad; }
+ }
+ return;
+
+ bad:;
+ int logfd = -1;
+ FILE *logf = 0;
+
+ logfd = open("/var/log/exec-sigignblock.log", O_APPEND|O_WRONLY);
+ if (logfd < 0)
+ if (errno == ENOENT || errno == EACCES || errno == EPERM)
+ return;
+
+ logf = fdopen(logfd, "a");
+ if (!logf) goto fail;
+ logfd = -1; /* eaten by fdopen */
+
+ unsigned long ourpid = getpid();
+ unsigned long ppid = getppid();
+ char parentbuf[100];
+
+ snprintf(parentbuf, sizeof(parentbuf), "/proc/%lu/exe", ppid);
+ r = readlink(parentbuf, parentbuf, sizeof(parentbuf)-1);
+ if (r < 0) {
+ const char *m = strerror(errno);
+ strncpy(parentbuf, m, sizeof(parentbuf)-1);
+ parentbuf[sizeof(parentbuf)-1] = 0;
+ } else if (r == 0) {
+ strcpy(parentbuf, "\"\"");
+ } else {
+ parentbuf[r] = 0;
+ }
+
+ time_t now;
+ now = time(NULL);
+ if (now == (time_t)-1) { errno = EIO; goto fail; }
+
+ struct tm *gmt = gmtime(&now);
+ if (!gmt) goto fail;
+
+ r = fprintf(logf, "%04d-%02d-%02d %02d:%02d:%02d UTC:"
+ "%s[%lu] execd oddly (parent %s[%lu]): %s: %s\n",
+ gmt->tm_year+1900, gmt->tm_mon, gmt->tm_mday,
+ gmt->tm_hour, gmt->tm_min, gmt->tm_sec,
+ argv0, ourpid,
+ parentbuf, ppid,
+ sig ? strsignal(sig) : "sigprocmask", oddity);
+ if (r < 0) goto fail;
+
+ r = fclose(logf);
+ logf = 0;
+ if (r) goto fail;
+
+ return;
+
+ fail:
+ perror("__libc_check_sigpipe report oddity");
+ if (logf) fclose(logf);
+ if (logfd>=0) close(logfd);
+ return;
+}
+
void
__libc_init_first (int argc, char **argv, char **envp)
{
@@ -96,6 +182,8 @@ _init (int argc, char **argv, char **envp)
#if defined SHARED && !defined NO_CTORS_DTORS_SECTIONS
__libc_global_ctors ();
#endif
+
+ __libc_check_sigpipe (argv[0]);
}
/* This function is defined here so that if this file ever gets into
diff --git a/debian/changelog b/debian/changelog
index f552f26..33a6254 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+glibc (2.22-7+iwj) UNRELEASED; urgency=medium
+
+ * SIGPIPE tracking
+
+ -- Ian Jackson <ijack...@chiark.greenend.org.uk> Sun, 08 May 2016 12:43:46 +0100
+
glibc (2.22-7) unstable; urgency=medium
[ Samuel Thibault ]
diff --git a/debian/shlibs-add-udebs b/debian/shlibs-add-udebs
old mode 100644
new mode 100755
2016-04-08 12:13:21 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[12813]
execd oddly (parent /usr/bin/dbus-daemon[12790]): Broken pipe: SIG_IGN
2016-04-08 12:13:21 UTC:/usr/lib/x86_64-linux-gnu/systemd-shim[12813] execd
oddly (parent /usr/bin/dbus-daemon[12790]): Broken pipe: SIG_IGN
2016-04-08 12:13:21 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[12911]
execd oddly (parent /usr/bin/dbus-daemon[12905]): Broken pipe: SIG_IGN
2016-04-08 12:13:21 UTC:/usr/lib/NetworkManager/nm-dispatcher[12911] execd
oddly (parent /usr/bin/dbus-daemon[12905]): Broken pipe: SIG_IGN
2016-04-08 12:13:24 UTC:/run/cgmanager/agents/cgm-release-agent.systemd[13682]
execd oddly (parent No such file or directory[2]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[2826] execd
oddly (parent /usr/bin/dbus-daemon[2824]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/lib/systemd/systemd-hostnamed[2826] execd oddly
(parent /usr/bin/dbus-daemon[2824]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[2915] execd
oddly (parent /usr/bin/dbus-daemon[2913]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/NetworkManager/nm-dispatcher[2915] execd oddly
(parent /usr/bin/dbus-daemon[2913]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:(pinger)[3213] execd oddly (parent
/usr/sbin/squid[3079]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/sbin/exim4[3250] execd oddly (parent
/usr/sbin/exim4[3248]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[3312] execd
oddly (parent /usr/bin/dbus-daemon[3311]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/bin/sh[3312] execd oddly (parent
/usr/bin/dbus-daemon[3311]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:mkdir[3317] execd oddly (parent /bin/dash[3312]):
Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/lib/systemd/systemd-logind[3312] execd oddly (parent
/usr/bin/dbus-daemon[3311]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[3327] execd
oddly (parent /usr/bin/dbus-daemon[3326]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/x86_64-linux-gnu/systemd-shim[3327] execd
oddly (parent /usr/bin/dbus-daemon[3326]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/bin/sh[3344] execd oddly (parent
/usr/sbin/lightdm[3294]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/xorg/Xorg[3344] execd oddly (parent
/usr/sbin/lightdm[3294]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[3348] execd
oddly (parent /usr/bin/dbus-daemon[3347]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/dbus-1.0/dbus-daemon-launch-helper[3350] execd
oddly (parent /usr/bin/dbus-daemon[3349]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/lib/policykit-1/polkitd[3348] execd oddly (parent
/usr/bin/dbus-daemon[3347]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/sbin/wpa_supplicant[3350] execd oddly (parent
/usr/bin/dbus-daemon[3349]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:sh[3471] execd oddly (parent /usr/lib/xorg/Xorg[3344]):
Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/bin/xkbcomp[3473] execd oddly (parent
/bin/dash[3471]): Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:sh[3530] execd oddly (parent /usr/lib/xorg/Xorg[3344]):
Broken pipe: SIG_IGN
2016-04-08 12:15:12 UTC:/usr/bin/xkbcomp[3531] execd oddly (parent
/bin/dash[3530]): Broken pipe: SIG_IGN
2016-04-08 12:15:13 UTC:lightdm[3713] execd oddly (parent
/usr/sbin/lightdm[3294]): Broken pipe: SIG_IGN
2016-04-08 12:15:15 UTC:/usr/lib/NetworkManager/nm-dhcp-helper[3976] execd
oddly (parent /sbin/dhclient[3952]): Broken pipe: SIG_IGN
2016-04-08 12:15:15 UTC:/usr/lib/NetworkManager/nm-dhcp-helper[4026] execd
oddly (parent /sbin/dhclient[3952]): Broken pipe: SIG_IGN
2016-04-08 12:15:16 UTC:lightdm[4148] execd oddly (parent
/usr/sbin/lightdm[3294]): Broken pipe: SIG_IGN
2016-04-08 12:15:20 UTC:lightdm[4155] execd oddly (parent
/usr/sbin/lightdm[3294]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/gnome-keyring-daemon[4160] execd oddly (parent
Permission denied[4155]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/bin/sh[4164] execd oddly (parent Permission
denied[4155]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:touch[4165] execd oddly (parent /bin/dash[4164]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:chmod[4166] execd oddly (parent /bin/dash[4164]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:date[4167] execd oddly (parent /bin/dash[4164]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:tempfile[4168] execd oddly (parent /bin/dash[4164]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:rm[4169] execd oddly (parent /bin/dash[4164]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:run-parts[4170] execd oddly (parent /bin/dash[4164]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:cat[4171] execd oddly (parent /bin/dash[4164]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:run-parts[4172] execd oddly (parent /bin/dash[4164]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:xrdb[4173] execd oddly (parent /bin/dash[4164]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:sh[4174] execd oddly (parent /usr/bin/xrdb[4173]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/cpp[4175] execd oddly (parent
/bin/dash[4174]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/lib/gcc/x86_64-linux-gnu/5/cc1[4176] execd oddly
(parent /usr/bin/cpp-5[4175]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:id[4177] execd oddly (parent /bin/dash[4164]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:xhost[4178] execd oddly (parent /bin/dash[4164]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:basename[4180] execd oddly (parent /bin/dash[4179]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:cut[4181] execd oddly (parent /bin/dash[4179]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/xdg-user-dirs-update[4183] execd oddly (parent
/bin/dash[4164]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/dbus-launch[4184] execd oddly (parent
/bin/dash[4164]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/xbrlapi[4182] execd oddly (parent
/bin/dash[4164]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/dbus-daemon[4186] execd oddly (parent
/usr/bin/dbus-launch[4185]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/unclutter[4189] execd oddly (parent
/bin/dash[4164]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:dbus-update-activation-environment[4190] execd oddly
(parent /bin/dash[4164]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/ssh-agent[4164] execd oddly (parent Permission
denied[4155]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/bin/bash[4164] execd oddly (parent Permission
denied[4155]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:hostname[4193] execd oddly (parent /bin/bash[4192]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:rm[4194] execd oddly (parent /bin/bash[4164]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/bin/sh[4195] execd oddly (parent /bin/bash[4164]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:hostname[4196] execd oddly (parent /bin/dash[4195]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:cat[4197] execd oddly (parent /bin/dash[4195]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:/usr/bin/perl[4198] execd oddly (parent
/bin/dash[4195]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:tee[4199] execd oddly (parent /bin/dash[4195]): Broken
pipe: SIG_IGN
2016-04-08 12:15:22 UTC:xauth[4200] execd oddly (parent /usr/bin/perl[4198]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:xdpyinfo[4201] execd oddly (parent
/usr/bin/perl[4198]): Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:uname[4202] execd oddly (parent /usr/bin/perl[4198]):
Broken pipe: SIG_IGN
2016-04-08 12:15:22 UTC:rm[4203] execd oddly (parent /bin/dash[4195]): Broken
pipe: SIG_IGN
