Bug 17019

Summary: gethostbyname call SIGSEGVs
Product: [Retired] Red Hat Raw Hide Reporter: Dmitry V. Levin <redhat>
Component: glibcAssignee: Jakub Jelinek <jakub>
Status: CLOSED ERRATA QA Contact:
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Priority: high    
Version: 1.0   
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OS: Linux   
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Last Closed: 2000-09-01 11:59:29 UTC Type: ---
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Description Dmitry V. Levin 2000-08-28 00:07:10 UTC 
While using glibc-2.1.92-5, I've noticed, that in certain conditions
call of gethostbyname function SIGSEGVs in function
_nss_files_gethostbyname_r.
Most easy way to reproduce it is to place into /etc/hosts to identic lines
which define traslation of some ipaddr into name with aliases, for example,
1.2.3.4	x	y
or, most commonly used,
127.0.0.1	localhost.localdomain	localhost

(first resolving rule for hosts in /etc/nsswitch.conf is files).
Comment 1 Jakub Jelinek 2000-09-01 10:41:33 UTC 
I cannot reproduce this.
My /etc/hosts has now:
127.0.0.1               localhost.localdomain localhost
127.0.0.1               localhost.localdomain localhost
127.0.0.1               localhost.localdomain localhost
127.0.0.1               localhost.localdomain localhost
1.2.3.4                 blabla
and ping blabla nor ping localhost causes any segfaults (nsswitch.conf starts
with files for hosts). Can you tell me which exact program should trigger it,
with what arguments?
Comment 2 Dmitry V. Levin 2000-09-01 11:59:27 UTC 
Well, my /etc/hosts now contain
1.2.3.4		x	y
1.2.3.4		x	y
(Duplicated lines are necessary to reproduce the bug.)

Here is a test program which causes segfault when executed:

#include <netdb.h>
int main( int ac, const char *av[] )
{
    if ( ac < 2 ) return 1;
    gethostbyname( av[1] );
    return 0;
}

$ gcc -g -O0 gethostbyname.c -o gethostbyname
$ ./gethostbyname x
Segmentation fault

"ping x" also sigsegvs.

Tested with glibc-2.1.92-5 and glibc-2.1.92-13.

gdb backtrace (glibc-2.1.92-13) is following:
Program received signal SIGSEGV, Segmentation fault.
#0  0x23bda9 in _nss_files_gethostbyname_r (name=0xbffffafd "x",
result=0xbffff7e8, 
    buffer=0x8049578 "\001\002\003\004", buflen=1024, errnop=0x233fa0,
herrnop=0xbffff918)
    at nss_files/files-hosts.c:262
#1  0x2077d6 in __gethostbyname_r (name=0xbffffafd "x", resbuf=0x236000,
buffer=0x8049578 "\001\002\003\004", 
    buflen=1024, result=0xbffff910, h_errnop=0xbffff918) at
../nss/getXXbyYY_r.c:189
#2  0x206573 in gethostbyname (name=0xbffffafd "x") at ../nss/getXXbyYY.c:141
#3  0x8048404 in main (ac=2, av=0xbffff9a4) at gethostbyname.c:6
#4  0x14c89e in __libc_start_main (main=0x80483e0 <main>, argc=2,
ubp_av=0xbffff9a4, init=0x80482a0 <_init>, 
    fini=0x8048454 <_fini>, rtld_fini=0x11c9d4 <_dl_fini>, stack_end=0xbffff99c)
    at ../sysdeps/generic/libc-start.c:111