Running Valgrind on my program generates an invalid read of size 4 error. I'm trying to locate it, but can't seem to find it.
#define _GNU_SOURCE
#include <stdio.h>
#include <netdb.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <sys/types.h>
#include <sys/socket.h>
void download_file (void){
int ret;
char *service = "http";
char *site = "www.sony.com";
char *page = "/";
char *msg;
struct addrinfo *res;
struct addrinfo hints;
const char * format = "GET %s HTTP/1.1\r\nHost: %s\r\nUser-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:30.0) Gecko/20100101 Firefox/30.0\r\n\r\n";
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
asprintf(&msg, format, page, site);
if((ret = getaddrinfo(site, service, &hints, &res)) != 0){
fprintf(stderr, "download_file: getaddrinfo error: %s\n", gai_strerror(ret));
freeaddrinfo(res);
free(msg);
return;
}
freeaddrinfo(res);
free(msg);
return;
}
int main (void){
download_file();
exit(0);
}
Here is the output from Valgrind:
==3215== Memcheck, a memory error detector
==3215== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==3215== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==3215== Command: ./a.out
==3215==
==3215== Invalid read of size 4
==3215== at 0x401718C: strlen (strlen.S:53)
==3215== by 0x4012F1F: _dl_open (dl-open.c:672)
==3215== by 0x495982F: do_dlopen (dl-libc.c:86)
==3215== by 0x400F0BF: _dl_catch_error (dl-error.c:178)
==3215== by 0x4959917: dlerror_run (dl-libc.c:47)
==3215== by 0x495997F: __libc_dlopen_mode (dl-libc.c:160)
==3215== by 0x4935447: __nss_lookup_function (nsswitch.c:434)
==3215== by 0x493569B: __nss_lookup (nsswitch.c:229)
==3215== by 0x493DB93: getservbyname_r@@GLIBC_2.4 (getXXbyYY_r.c:203)
==3215== by 0x48FDBA3: gaih_inet_serv (getaddrinfo.c:164)
==3215== by 0x48FE917: gaih_inet (getaddrinfo.c:332)
==3215== by 0x490145F: getaddrinfo (getaddrinfo.c:2438)
==3215== Address 0x4988e64 is 44 bytes inside a block of size 46 alloc'd
==3215== at 0x4835978: malloc (vg_replace_malloc.c:263)
==3215== by 0x400EE03: _dl_signal_error (dl-error.c:90)
==3215== by 0x400903F: _dl_map_object (dl-load.c:2556)
==3215== by 0x4013157: dl_open_worker (dl-open.c:226)
==3215== by 0x400F0BF: _dl_catch_error (dl-error.c:178)
==3215== by 0x4012C9B: _dl_open (dl-open.c:633)
==3215== by 0x495982F: do_dlopen (dl-libc.c:86)
==3215== by 0x400F0BF: _dl_catch_error (dl-error.c:178)
==3215== by 0x4959917: dlerror_run (dl-libc.c:47)
==3215== by 0x495997F: __libc_dlopen_mode (dl-libc.c:160)
==3215== by 0x4935447: __nss_lookup_function (nsswitch.c:434)
==3215== by 0x493569B: __nss_lookup (nsswitch.c:229)
==3215==
==3215==
==3215== HEAP SUMMARY:
==3215== in use at exit: 0 bytes in 0 blocks
==3215== total heap usage: 67 allocs, 67 frees, 6,461 bytes allocated
==3215==
==3215== All heap blocks were freed -- no leaks are possible
==3215==
==3215== For counts of detected and suppressed errors, rerun with: -v
==3215== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 25 from 11)
Can someone please help me understand why this error occurs? Or how to correct it? In my searches I am only finding errors related to the gethostbyaddr().
It looks like the invalid read error is coming from getaddrinfo(), but I'm unable to locate the file getaddrinfo.c on my system to try and correct it.
This looks like a problem similar to one discussed here: http://git.661346.n2.nabble.com/PATCH-valgrind-ignore-SSE-based-strlen-invalid-reads-td6175816.html
An optimized strlen() often reads full words when searching for the null terminator char. This can be done by an implementation in a safe way, even if it technically violates an allocation boundary.
It might be that you need a newer version of valgrind (3.9.0 is current) or valgrind needs to be configured or patched for the runtime you're using. You might want to configure a suppression for this: http://valgrind.org/docs/manual/manual-core.html#manual-core.suppress