[Bug libc/4067] New: possible problem in sigaction resulting into segfault

[Bug libc/4067] New: possible problem in sigaction resulting into segfault

[nico-linux-glibc at schottelius dot org]

When sa.sa_flags is not set my program segfaults after the handler for sig_child
was called.

I don't think this should be the case.

Having undefined 

Code:
http://unix.schottelius.org/cgi-bin/gitweb.cgi?p=cLinux/cinit.git;a=blob;h=fc744794e5f486cd6ac9d9b04417289e3710fd18;hb=7077199ab69bd9c5760049b71b6ed3c28aafcb87;f=src/core/set_signals.c

Errors in valgrind:
http://home.schottelius.org/~nico/unix/progs/cinit/problem-2007-02-15.valgrind

Description / Tests I did before:
http://home.schottelius.org/~nico/unix/progs/cinit/problem-2007-02-15

I am using 2.3.6.ds1-11 on debian/sid.

-- 
           Summary: possible problem in sigaction resulting into segfault
           Product: glibc
           Version: 2.3.6
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: nico-linux-glibc at schottelius dot org
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=4067

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[Bug libc/4067] possible problem in sigaction resulting into segfault

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2007-02-16 22:52 -------
File this with your distribution.  I'm not going to look into any ancient libc
as a replacement for support the distribution does want to provide.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WORKSFORME


http://sourceware.org/bugzilla/show_bug.cgi?id=4067

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[Bug libc/4067] possible problem in sigaction resulting into segfault

[nico-linux-glibc at schottelius dot org]

------- Additional Comments From nico-linux-glibc at schottelius dot org  2007-02-17 16:38 -------
same happens on glibc-2.4-7mdv2007.0:

[...]
testC
=> cinit started.
test2 - es scheint zu gehen
[SERVICE] /etc/cinit/svc/init: [ FAILED] Service failed!
Finished CHILD catcher
Segmentation fault

If I init the sa.flags it does not segfault:

[telmich@jonas src]$ diff -u core/set_signals.c.segfault core/set_signals.c    
     
--- core/set_signals.c.segfault	2007-02-17 16:34:39.000000000 +0100
+++ core/set_signals.c	2007-02-17 16:34:46.000000000 +0100
@@ -18,17 +18,17 @@
 
    if(action == ACT_SERV) {
       sa.sa_handler  = sig_child;
-//      sa.sa_flags    = SA_NOCLDSTOP; 
+      sa.sa_flags    = SA_NOCLDSTOP; 
    } else {
       sa.sa_handler=SIG_DFL;
-//      sa.sa_flags    = 0;
+      sa.sa_flags    = 0;
    }
-//   sigemptyset(&sa.sa_mask);
+   sigemptyset(&sa.sa_mask);
 
    sigaction(SIGCHLD,&sa,NULL);     /* what todo when a child exited    */
 
    /* reset flags */
-//   sa.sa_flags    = 0;
+   sa.sa_flags    = 0;
    if(action == ACT_SERV) {
       sa.sa_handler=do_reboot;
    }


The version:

[telmich@jonas src]$ /lib/libc.so.6 
GNU C Library development release version 2.4, by Roland McGrath et al.
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.1.1 20060724 (prerelease) (4.1.1-3mdk).
Compiled on a Linux 2.6.17 system on 2007-01-18.
Available extensions:
	crypt add-on version 2.1 by Michael Glad and others
	GNU libio by Per Bothner
	NIS(YP)/NIS+ NSS modules 0.19 by Thorsten Kukuk
	Native POSIX Threads Library by Ulrich Drepper et al
	BIND-8.2.3-T5B
Thread-local storage support included.
For bug reporting instructions, please see:
<http://www.gnu.org/software/libc/bugs.html>.



-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|WORKSFORME                  |
            Version|2.3.6                       |2.4


http://sourceware.org/bugzilla/show_bug.cgi?id=4067

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[Bug libc/4067] possible problem in sigaction resulting into segfault

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2007-02-17 18:14 -------
Report it to the distribution.  glibc 2.4 is ancient and not supported here.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=4067

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[Bug libc/4067] possible problem in sigaction resulting into segfault

[nico-linux-glibc at schottelius dot org]

------- Additional Comments From nico-linux-glibc at schottelius dot org  2007-02-17 19:40 -------
Damn, you are right, glibc 2.5 works:

zellis% /lib/libc.so.6 
GNU C Library stable release version 2.5, by Roland McGrath et al.

Btw, perhaps you should add 2.5 to the version list so one does not assume 2.4
is the latest when one sees the available versions in bugzilla.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |VERIFIED


http://sourceware.org/bugzilla/show_bug.cgi?id=4067

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[Bug libc/4067] possible problem in sigaction resulting into segfault

[nico-linux-glibc at schottelius dot org]

------- Additional Comments From nico-linux-glibc at schottelius dot org  2007-02-17 19:53 -------
Sorry, used the wrong version with initialized flags. glibc-2.5 also segfaults,
if sa.flags is uninitialized. Use this code to reproduce:

---------------------------
   struct sigaction sa;
   
   if(action == ACT_SERV) {
      sa.sa_handler  = sig_child;
//      sa.sa_flags    = SA_NOCLDSTOP; 
   } else {
      sa.sa_handler=SIG_DFL;
//      sa.sa_flags    = 0;
   }
//   sigemptyset(&sa.sa_mask);

   sigaction(SIGCHLD,&sa,NULL);     /* what todo when a child exited    */

---------------------------

And then fork() away and tada: segfault _after_ the sigchild handler exits.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|VERIFIED                    |REOPENED
         Resolution|FIXED                       |


http://sourceware.org/bugzilla/show_bug.cgi?id=4067

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[Bug libc/4067] possible problem in sigaction resulting into segfault

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2007-02-17 21:51 -------
What do you expect if you pass uninitialized data?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |INVALID


http://sourceware.org/bugzilla/show_bug.cgi?id=4067

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[Bug libc/4067] possible problem in sigaction resulting into segfault

[nico-linux-glibc at schottelius dot org]

------- Additional Comments From nico-linux-glibc at schottelius dot org  2007-02-18 01:02 -------
I expect sigaction to return an error or to ignore invalid setting, not silently
to accept the input.

I am wondering, how an unintialised integer that simply sets flags makes glibc
to segfault.


-- 


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