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[Bug libc/10484] New: getaddrinfo segfaults if /etc/hosts has a long line
- From: "lars at ubuntu dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 5 Aug 2009 15:22:29 -0000
- Subject: [Bug libc/10484] New: getaddrinfo segfaults if /etc/hosts has a long line
- Reply-to: sourceware-bugzilla at sourceware dot org
If /etc/hosts contains a long line (thousands of bytes), getaddrinfo causes a
segmentation fault. A small program to test:
-- 8< ---
#include <stddef.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
int main(void)
{
struct addrinfo *result;
getaddrinfo("localhost", NULL, NULL, &result);
return 0;
}
--- 8< ---
On a system with short lines in /etc/hosts, the above program exits normally. If
/etc/hosts has a very long line (5500 bytes is sufficiently long), it
segmentation faults.
I think this is due to using alloca and extend_alloca to hold the line when
parsing the file, which leads to a stack overflow, which then results in the
kernel sending a SIGSEGV to the program. The parsing code is not set up to
handle that. Unfortunately, I am too stupid to provide a patch to fix this.
My test /etc/hosts file has IPv6 addresses commented out, so the segmentation
fault happens in sysdeps/posix/getaddrinfo.c, function gaih_inet, around line
531, on this line:
rc = __gethostbyname2_r (name, family, &th, tmpbuf,
tmpbuflen, &h, &herrno);
My stack limit is 8 megabytes.
This was originally filed as a bug in Ubuntu, and applies to both versions 2.9
and 2.10 in that distribution. I have compared the source file against the
current version in git, and it has no relevant changes. (I was unable to set up
a chroot to actually test the current git version, sorry.)
Original bug: https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/386791
--
Summary: getaddrinfo segfaults if /etc/hosts has a long line
Product: glibc
Version: 2.9
Status: NEW
Severity: minor
Priority: P2
Component: libc
AssignedTo: drepper at redhat dot com
ReportedBy: lars at ubuntu dot com
CC: glibc-bugs at sources dot redhat dot com
GCC build triplet: x86_64-unknown-linux-gnu
GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu
http://sourceware.org/bugzilla/show_bug.cgi?id=10484
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