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On 2012-01-13T16:38:09+00:00 Aj-suse wrote:

I have seen some reports where glibc crashes if nscd is not running,
especially with chromium but also with ktorrent. This is not always
reproduceable, so there's some kind of race or random memory corruption.

valgrind reports:
==16750== Process terminating with default action of signal 11 (SIGSEGV)
==16750==  Access not within mapped region at address 0x17
==16750==    at 0xC63DC1E: __nscd_get_mapping (in /lib64/libc-2.15.so)
==16750==    by 0xC63DDE3: __nscd_get_map_ref (in /lib64/libc-2.15.so)
==16750==    by 0xC63B2E1: nscd_gethst_r (in /lib64/libc-2.15.so)
==16750==    by 0xC63BB96: __nscd_gethostbyname2_r (in /lib64/libc-2.15.so)
==16750==    by 0xC6213F0: gethostbyname2_r@@GLIBC_2.2.5 (in 
/lib64/libc-2.15.so)
==16750==    by 0xC5F5D8F: gaih_inet (in /lib64/libc-2.15.so)
==16750==    by 0xC5F6ED2: getaddrinfo (in /lib64/libc-2.15.so)
==16750==    by 0x140E7BD: net::SystemHostResolverProc(std::string const&, 
net::AddressFamily, int, net::AddressList*, int*) (in 
/usr/lib64/chromium/chromium)
==16750==    by 0x1407C57: net::HostResolverImpl::Job::DoLookup(base::TimeTicks 
const&, unsigned int) (in /usr/lib64/chromium/chromium)
==16750==    by 0x2B5B2FA: base::(anonymous 
namespace)::WorkerThread::ThreadMain() (in /usr/lib64/chromium/chromium)
==16750==    by 0x11753C1: base::(anonymous namespace)::ThreadFunc(void*) (in 
/usr/lib64/chromium/chromium)
==16750==    by 0x919FF65: start_thread (in /lib64/libpthread-2.15.so)

gdb gives a similar backtrace.

After reverting commit 3a2c02424d9824f5cdea4ebd32ff929b2b1f49c6, the
problem does not appear anymore.

I can't reproduce it yet on my system - so no further information.

Reports:
https://bugzilla.novell.com/show_bug.cgi?id=741021
https://bbs.archlinux.org/viewtopic.php?id=133021

Reply at: https://bugs.launchpad.net/eglibc/+bug/929219/comments/0

------------------------------------------------------------------------
On 2012-02-07T16:44:47+00:00 ajaxas wrote:

I confirm this for Chromium on archlinux.

Specs (just in case):
- kernel 3.3-rc2 (vanilla)
- glibc 2.15

I can only add 2 things:
- this happens only once in a session, i.e. when Chromium is launched for the 
first time after boot; after that Chromium starts normally.
- I couldn't yet reproduce this bug *within* gdb - it always starts without a 
problem. I will continue trying though.

Reply at: https://bugs.launchpad.net/eglibc/+bug/929219/comments/1

------------------------------------------------------------------------
On 2012-02-11T22:52:36+00:00 Pcpa wrote:

I am just starting testing an update from "2.14.90" to "2.15" for
mandriva, and I get this randomly, varying from 1 to 4 times every
restart of chromium-browser.

$ rpm -qf /usr/bin/chromium-browser 
chromium-browser-unstable-17.0.963.26-1-mdv2012.0.x86_64

$ LD_LIBRARY_PATH=/usr/lib64/chromium-browser gdb 
/usr/lib64/chromium-browser/chrome
...
0x00007ffff18f5e7e in __nscd_get_mapping (type=<optimized out>, key=
    0x7ffff19436b4 "hosts", mappedp=0x7ffff1b82548) at nscd_helper.c:417
417       if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
(gdb) p oldval
$1 = (struct mapped_database *) 0xffffffffffffffff
(gdb) bt
#0  0x00007ffff18f5e7e in __nscd_get_mapping (type=<optimized out>, key=
    0x7ffff19436b4 "hosts", mappedp=0x7ffff1b82548) at nscd_helper.c:417
#1  0x00007ffff18f4098 in __nscd_get_nl_timestamp () at nscd_gethst_r.c:113
#2  0x00007ffff18e2be8 in __check_pf (seen_ipv4=0x7ffff7ed071e, seen_ipv6=
    0x7ffff7ed071f, in6ai=0x7ffff7ed06e0, in6ailen=0x7ffff7ed06f0)
    at ../sysdeps/unix/sysv/linux/check_pf.c:324
#3  0x00007ffff18aa015 in __GI_getaddrinfo (name=
    0x555559ba3a68 "www.statcounter.com", service=<optimized out>, hints=
    0x7ffff7ed0a60, pai=0x7ffff7ed0a98) at ../sysdeps/posix/getaddrinfo.c:2305
#4  0x00005555566a0c9c in ?? ()
#5  0x000055555669b3e8 in ?? ()
#6  0x0000555557d85b95 in ?? ()
#7  0x0000555556437fb2 in ?? ()
#8  0x00007ffff4239bd0 in start_thread (arg=0x7ffff7ed1700)
    at pthread_create.c:309
#9  0x00007ffff18bd93d in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115

I believe this should correct it, but not the proper solution:

--- glibc-2.15-a316c1f/nscd/nscd_helper.c.orig  2012-02-11 20:25:37.804514879 
-0200
+++ glibc-2.15-a316c1f/nscd/nscd_helper.c       2012-02-11 20:26:07.428588082 
-0200
@@ -414,7 +414,8 @@ __nscd_get_mapping (request_type type, c
   struct mapped_database *oldval = *mappedp;
   *mappedp = result;
 
-  if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
+  if (oldval != NULL && oldval != NO_MAPPING
+      && atomic_decrement_val (&oldval->counter) == 0)
     __nscd_unmap (oldval);
 
   return result;


hopefully also useful:

(gdb) frame 0#0  0x00007ffff18f5e7e in __nscd_get_mapping (type=<optimized 
out>, key=
    0x7ffff19436b4 "hosts", mappedp=0x7ffff1b82548) at nscd_helper.c:417
417       if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
(gdb) p keylen
$12 = 6
(gdb) p mapsize
$13 = 0
(gdb) p iov
$14 = {{iov_base = 0x7ffff7ed0330, iov_len = 6}, {iov_base = 0x7ffff7ed04a0, 
    iov_len = 8}}
(gdb) p cmsg
$15 = <optimized out>
(gdb) p (cmsg)->__cmsg_data
value has been optimized out
(gdb) p ip
$16 = <optimized out>
(gdb) p mapfd
$17 = <optimized out>
(gdb) p st
No symbol "st" in current context.
(gdb) p mapping
$18 = <optimized out>
(gdb) p size
No symbol "size" in current context.
(gdb) p oldval
$19 = (struct mapped_database *) 0xffffffffffffffff
(gdb) p result
$20 = (struct mapped_database *) 0xffffffffffffffff

Reply at: https://bugs.launchpad.net/eglibc/+bug/929219/comments/8

------------------------------------------------------------------------
On 2012-02-11T23:01:24+00:00 Pcpa wrote:

Forgot to add some extra information:

$ ls /usr/lib64/chromium-browser
chrome*            libppGoogleNaClPluginChrome.so*  resources.pak
chrome.pak         locales/                         themes/
chrome-sandbox*    nacl_helper*                     xdg-mime*
chromium-wrapper*  nacl_helper_bootstrap*           xdg-settings*
default_apps/      nacl_irt_x86_64.nexe
libffmpegsumo.so*  resources/

If removing libppGoogleNaClPluginChrome.so from that directory,
or overriding the wrapper and starting chrome without setting
LD_LIBRARY_PATH I could not get it to crash, neither did notice
any problems.

Reply at: https://bugs.launchpad.net/eglibc/+bug/929219/comments/9

------------------------------------------------------------------------
On 2012-02-12T04:25:56+00:00 ajaxas wrote:

It's already fixed in archlinux, though it was one helluva big commit:
http://projects.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/glibc&id=8e950112da65c96ad17cbd650ac9db3050343a3f
I'm not even sure where to look...

Reply at: https://bugs.launchpad.net/eglibc/+bug/929219/comments/10

------------------------------------------------------------------------
On 2012-02-12T04:33:38+00:00 Allan McRae wrote:

That is called reverting the commit that caused the issue...  Not fixing
it.

Reply at: https://bugs.launchpad.net/eglibc/+bug/929219/comments/11

------------------------------------------------------------------------
On 2012-02-12T04:39:26+00:00 ajaxas wrote:

(In reply to comment #5)
> That is called reverting the commit that caused the issue...  Not fixing it.

Okay.
It's already reverted in archlinux. Hope this stays reverted for good and finds 
it's way into the upstream (if this wasn't archlinux-only problem since it was 
*package* version that changed...)

Reply at: https://bugs.launchpad.net/eglibc/+bug/929219/comments/12


** Changed in: glibc
       Status: Unknown => Confirmed

** Changed in: eglibc
       Status: Unknown => Confirmed

** Changed in: glibc
   Importance: Unknown => Medium

** Changed in: eglibc
   Importance: Unknown => Medium

** Bug watch added: Novell/SUSE Bugzilla #741021
   https://bugzilla.novell.com/show_bug.cgi?id=741021

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Title:
  chromium-browser crashed with SIGSEGV in __nscd_get_mapping()

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