[linux] Upgrading glibc for the GHOST Vulnerability

1> Test if the problem exists, code:

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#define CANARY "in_the_coal_mine"

struct {
    char buffer[1024];
    char canary[sizeof(CANARY)];
} temp = { "buffer", CANARY };

int main(void) {
    struct hostent resbuf;
    struct hostent *result;
    int herrno;
    int retval;

    /*** strlen (name) = size_needed - sizeof (*host_addr) - sizeof (*h_addr_ptrs) - 1; ***/
    size_t len = sizeof(temp.buffer) - 16*sizeof(unsigned char) - 2*sizeof(char *) - 1;
    char name[sizeof(temp.buffer)];
    memset(name, ‘0‘, len);
    name[len] = ‘\0‘;

    retval = gethostbyname_r(name, &resbuf, temp.buffer, sizeof(temp.buffer), &result, &herrno);

    if (strcmp(temp.canary, CANARY) != 0) {
        puts("vulnerable");
        exit(EXIT_SUCCESS);
    }
    if (retval == ERANGE) {
        puts("not vulnerable");
        exit(EXIT_SUCCESS);
    }
    puts("should not happen");
    exit(EXIT_FAILURE);
}

2> 编译测试代码

　　　　gcc code.c -o testGhost

　　　　./testGhost

　　　　vulnerable  or  not vulnerable

3> 升级

　　　　yum clean all　

　　　　yum update