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getaddrinfo: __resolv_conf_allocate: Assertion `conf == ptr' failed

Asked by Alberto Pires de Oliveira Neto

Hi, I have a code that needs to resolve a name to IP. This code is already working in a lot of different distros and versions for a long time, but when I try to run in a freshly installed Ubuntu 18.04.1 (4.15.0-34-generic #37-Ubuntu SMP Mon Aug 27 15:21:48 UTC 2018 x86_64 x86_64 x86_64), and my /etc/resolv.conf has a line "search anyname.???" where ??? can be any group of three letters I get the following error:

  Electric Fence 2.2 Copyright (C) 1987-1999 Bruce Perens <email address hidden>
Resolving for Host: <aaa>, Port: <5000>
resolv: resolv_conf.c:423: __resolv_conf_allocate: Assertion `conf == ptr' failed.
Aborted (core dumped)

It's also important to mention, that Electric Fence (-lefence) must be used.
I've included the code that causes the error, it happens when I call getaddrinfo

Thanks.

 char buffer[128];
 struct addrinfo hints;
 struct addrinfo *result, *rp;
 struct sockaddr_in *address;

 if (argc < 2) {
  printf("Error: Resolve <host> <port>\n");
  exit(1);
 }

 char *p = (char*) malloc(120);
 printf("Resolving for Host: <%s>, Port: <%s>\n", argv[1], argv[2]);

 memset(&hints, 0, sizeof(struct addrinfo));
 hints.ai_canonname = NULL;
 hints.ai_addr = NULL;
 hints.ai_next = NULL;
 //hints.ai_family = AF_UNSPEC;
 hints.ai_family = AF_INET;
 hints.ai_socktype = SOCK_STREAM;
 hints.ai_flags = AI_NUMERICSERV;

 if (getaddrinfo(argv[1], argv[2], &hints, &result) != 0) {
  printf("Failed to call getaddrinfo.\n");
  exit(1);
 }

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actionparsnip (andrew-woodhead666) said : 		#1

Are you using DHCP on the system or are you using a static IP?
Is the system fully updated?

Thanks

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Alberto Pires de Oliveira Neto (apon) said : 		#2

Yes, using dhcp. Apart from the extra development packages it was a standard installation.
And the system is fully updated. (Last update Sep 19/2018)

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Alberto Pires de Oliveira Neto (apon) said : 		#3

This last test was made on a VirtualBox installation, but I was already able to replicate this on two different computers with the same conditions.

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Alberto Pires de Oliveira Neto (apon) said : 		#4

Another update: I was suspecting of the glibc-2.27 (the one that is used on Ubuntu 18), so I've downloaded the glibc-2.27 on my Ubuntu 16.04-LTS and was able to replicate the problem as well.

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Alberto Pires de Oliveira Neto (apon) said : 		#5

Also, it is possible that it's something in the Electric Fence library (-lefence) since it's used for debug of memory allocation. Probably an issue with EFence and glibc-2.27.

I've debugged the resolv_conf.c and it seams that alloc_buffer_allocate() and alloc_buffer_alloc() should return the same pointer are not doing this:

resolv_conf.conf: 0x7f9f00f33f90
resolv_conf.ptr : 0x7f9f00f33f8c
resolv: resolv_conf.c:425: __resolv_conf_allocate: Assertion `conf == ptr' failed.

If I don't call malloc before calling getaddrinfo or do not use -lefence the problem doesn't happen.

I hope it helps, anyway I'll keep digging...

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Launchpad Janitor (janitor) said : 		#6

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

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Alexander Traud (traud) said : 		#7

I am facing the same assert while debugging openssl s_server. Thanks for the trick with removing ‘search’ from the file ‘/etc/resolv.conf’. Anyway, any news about this issue?

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Alberto Pires de Oliveira Neto (apon) said : 		#8

Not so far. It seams that a name with 8 or more characters before the dot works. Example:
search eexample.com

I've noticed also a message in my syslog:

systemd-resolved[1434]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.

I don't know yet if there is a connection, I'm still lost.

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Launchpad Janitor (janitor) said : 		#9

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

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Paul Sheer (paulsheer) said : 		#10

Hi,

The reason for this failure is probably because the Electric Fence (-lefence / libefence.so) library is returning non-aligned pointers from its malloc() function.

Hope this helps

Paul

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