when starting dmesg it sometimes segfaults. syslog shows: info kern kernel [2221086.384526] dmesg[32436]: segfault at 9d44014 ip b76110eb sp bf880b50 error 6 in libc-2.15.so[b759e000+144000] it happens often, not always, so i think it depends on which printk's should be displayed. other binaries are not affected. can be reproduced on >2 other gentoo-machines of mine (all different x86 hardware). After clearing the ring-buffer (-C) the problem disappears for now. i am using util-linux 2.21.2 . Reproducible: Sometimes Steps to Reproduce: 1. dmesg 2. 3. Actual Results: Segmentation fault Expected Results: kernel ring buffer output of "strace dmesg": execve("/bin/dmesg", ["dmesg"], [/* 37 vars */]) = 0 brk(0) = 0x95fd000 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7743000 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 fstat64(3, {st_mode=S_IFREG|0644, st_size=30521, ...}) = 0 mmap2(NULL, 30521, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb773b000 close(3) = 0 open("/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0000\246\1\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=1340640, ...}) = 0 mmap2(NULL, 1350172, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb75f1000 mmap2(0xb7735000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x144) = 0xb7735000 mmap2(0xb7738000, 10780, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7738000 close(3) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb75f0000 set_thread_area({entry_number:-1 -> 6, base_addr:0xb75f06c0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0 mprotect(0xb7735000, 8192, PROT_READ) = 0 mprotect(0x804d000, 4096, PROT_READ) = 0 mprotect(0xb7761000, 4096, PROT_READ) = 0 munmap(0xb773b000, 30521) = 0 brk(0) = 0x95fd000 brk(0x961e000) = 0x961e000 open("/usr/lib/locale/locale-archive", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3 fstat64(3, {st_mode=S_IFREG|0644, st_size=1853888, ...}) = 0 mmap2(NULL, 1853888, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb742b000 close(3) = 0 syslog(SYSLOG_ACTION_SIZE_BUFFER, 0, 0) = 131072 syslog(SYSLOG_ACTION_READ_ALL, "<7>[3748104.888492] netfilter dr"..., 131080) = 132083 open("/usr/lib/gconv/gconv-modules.cache", O_RDONLY) = -1 ENOENT (No such file or directory) open("/usr/lib/gconv/gconv-modules", O_RDONLY|O_CLOEXEC) = 3 fcntl64(3, F_GETFD) = 0x1 (flags FD_CLOEXEC) fstat64(3, {st_mode=S_IFREG|0644, st_size=56368, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7742000 read(3, "# GNU libc iconv configuration.\n"..., 4096) = 4096 --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x961e014} --- +++ killed by SIGSEGV +++ Segmentation fault emerge --info: Portage 2.1.11.50 (default/linux/x86/13.0, gcc-4.6.3, glibc-2.15-r3, 3.2.12-jason-core2-20120505 i686) ================================================================= System uname: Linux-3.2.12-jason-core2-20120505-i686-Intel-R-_Xeon-R-_CPU_5160_@_3.00GHz-with-gentoo-2.1 KiB Mem: 3375196 total, 103704 free KiB Swap: 0 total, 0 free Timestamp of tree: Sun, 10 Feb 2013 18:30:01 +0000 ld GNU ld (GNU Binutils) 2.22 app-shells/bash: 4.2_p37 dev-lang/python: 2.7.3-r2 dev-util/cmake: 2.8.9 dev-util/pkgconfig: 0.28 sys-apps/baselayout: 2.1-r1 sys-apps/openrc: 0.11.8 sys-apps/sandbox: 2.5 sys-devel/autoconf: 2.69 sys-devel/automake: 1.11.6 sys-devel/binutils: 2.22-r1 sys-devel/gcc: 4.6.3 sys-devel/gcc-config: 1.7.3 sys-devel/libtool: 2.4-r1 sys-devel/make: 3.82-r4 sys-kernel/linux-headers: 3.6 (virtual/os-headers) sys-libs/glibc: 2.15-r3 Repositories: gentoo x-portage ACCEPT_KEYWORDS="x86" ACCEPT_LICENSE="* -@EULA" CBUILD="i586-pc-linux-gnu" CFLAGS="-O2 -march=i586 -fomit-frame-pointer -pipe" CHOST="i586-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/share/openvpn/easy-rsa /var/bind" CONFIG_PROTECT_MASK="/etc/* /etc/ca-certificates.conf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/php/apache2-php5.3/ext-active/ /etc/php/cgi-php5.3/ext-active/ /etc/php/cli-php5.3/ext-active/ /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo" CXXFLAGS="-O2 -march=i586 -fomit-frame-pointer -pipe" DISTDIR="/var/portage/distfiles" FCFLAGS="-O2 -march=i686 -pipe" FEATURES="assume-digests binpkg-logs config-protect-if-modified distlocks ebuild-locks fixlafiles merge-sync news parallel-fetch protect-owned sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch" FFLAGS="-O2 -march=i686 -pipe" GENTOO_MIRRORS="http://distfiles.gentoo.org" LANG="C" LC_ALL="de_DE.UTF-8" LDFLAGS="-Wl,-O1 -Wl,--as-needed" MAKEOPTS="-j5" PKGDIR="/var/portage/packages" PORTAGE_CONFIGROOT="/" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/var/portage" PORTDIR_OVERLAY="/dat/local/share/portage" SYNC="rsync://rsync.gentoo.org/gentoo-portage" USE="alsa bzip2 cli cxx dri fortran gd iconv imap jpeg mbox modules mudflap mysql ncurses nptl openmp oss pam pcre perl png readline session ssl syslog tcpd tiff truetype unicode x86 xml zlib" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1 emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mmap_emul mulaw multi null plug rate route share shm softvol" APACHE2_MODULES="actions alias auth_basic auth_digest filter authn_default authn_file authz_default authz_groupfile authz_host authz_owner authz_user cgi deflate dir env expires headers include info log_config mime mime_magic proxy proxy_balancer proxy_connect proxy_http rewrite setenvif so status userdir unique_id vhost_alias" APACHE2_MPMS="prefork" CALLIGRA_FEATURES="kexi words flow plan sheets stage tables krita karbon braindump" CAMERAS="ptp2" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf superstar2 timing tsip tripmate tnt ubx" INPUT_DEVICES="keyboard mouse evdev" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" NGINX_MODULES_HTTP="access auth_basic charset fastcgi gzip limit_req map proxy rewrite ssl stub_status" PHP_TARGETS="php5-3" PYTHON_SINGLE_TARGET="python2_7" PYTHON_TARGETS="python2_7 python3_2" RUBY_TARGETS="ruby18 ruby19" USERLAND="GNU" VIDEO_CARDS="fbdev glint intel mach64 mga nouveau nv r128 radeon savage sis tdfx trident vesa via vmware dummy v4l" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account" Unset: CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, USE_PYTHON
I just tried dmesg from util-linux 2.22.2 directly from www.kernel.org, built in /tmp without portage for not breaking something - works without problems. dmesg.c from 2.22.2 is about 50% bigger, so something major seems to have changed.
and does the util-linux-2.22.2 ebuild (already in the tree) work ?
yes, 2.22.2 from portage works too. Usually i would like to avoid using ~x86 for core-packages in production environments. for a testing purpose i deleted "/usr/lib/gconv/gconv-modules" (the last successful open() in strace output above) on a test machine. results in: *** glibc detected *** dmesg: free(): invalid next size (normal): 0x0928a880 *** ======= Backtrace: ========= /lib/libc.so.6(+0x7066d)[0xb768866d] /lib/libc.so.6(+0x61879)[0xb7679879] /lib/libc.so.6(fopen+0x22)[0xb76798a2] /lib/libc.so.6(+0x1d2ba)[0xb76352ba] /lib/libc.so.6(+0x1c7cd)[0xb76347cd] /lib/libc.so.6(+0x8b24a)[0xb76a324a] /lib/libc.so.6(+0x8b392)[0xb76a3392] /lib/libc.so.6(mbrtowc+0x1bd)[0xb769918d] dmesg[0x804a0c8] ======= Memory map: ======== 08048000-0804d000 r-xp 00000000 08:02 85403 /.layer23/mnt/readonly/bin/dmesg 0804d000-0804e000 r--p 00004000 08:02 85403 /.layer23/mnt/readonly/bin/dmesg 0804e000-0804f000 rw-p 00005000 08:02 85403 /.layer23/mnt/readonly/bin/dmesg 0926a000-0928b000 rw-p 00000000 00:00 0 [heap] b742b000-b7448000 r-xp 00000000 08:02 118612 /.layer23/mnt/readonly/usr/lib/libgcc_s.so.1 b7448000-b7449000 r--p 0001c000 08:02 118612 /.layer23/mnt/readonly/usr/lib/libgcc_s.so.1 b7449000-b744a000 rw-p 0001d000 08:02 118612 /.layer23/mnt/readonly/usr/lib/libgcc_s.so.1 b7452000-b7617000 r--p 00000000 08:02 23558 /.layer23/mnt/readonly/usr/lib/locale/locale-archive b7617000-b7618000 rw-p 00000000 00:00 0 b7618000-b775c000 r-xp 00000000 08:02 23324 /.layer23/mnt/readonly/lib/libc-2.15.so b775c000-b775e000 r--p 00144000 08:02 23324 /.layer23/mnt/readonly/lib/libc-2.15.so b775e000-b775f000 rw-p 00146000 08:02 23324 /.layer23/mnt/readonly/lib/libc-2.15.so b775f000-b7762000 rw-p 00000000 00:00 0 b7769000-b776b000 rw-p 00000000 00:00 0 b776b000-b7787000 r-xp 00000000 08:02 23314 /.layer23/mnt/readonly/lib/ld-2.15.so b7787000-b7788000 r-xp 00000000 00:00 0 [vdso] b7788000-b7789000 r--p 0001c000 08:02 23314 /.layer23/mnt/readonly/lib/ld-2.15.so b7789000-b778a000 rw-p 0001d000 08:02 23314 /.layer23/mnt/readonly/lib/ld-2.15.so bfee3000-bff04000 rw-p 00000000 00:00 0 [stack] Aborted hope that helps.
dmesg -c or -C helps btw (as workaround).
(In reply to comment #3) > yes, 2.22.2 from portage works too. Usually i would good > like to avoid using ~x86 for core-packages in production environments. bug 458226 (In reply to comment #1) > I just tried dmesg from util-linux 2.22.2 directly from www.kernel.org, > built in /tmp without portage for not breaking something - works without > problems. good closing then because 2.22.2 is the current stable (or going stable for some arch's) wrt bug 458226
*** This bug has been marked as a duplicate of bug 452828 ***
