SIGABRT in C Linux

Question

i received an strange SIGABRT in my C program, tha's my function where the problem appears:

int get_interface_mac_addr(Interface* iface) {
    char arquivo[10];
    sprintf(arquivo, "/sys/class/net/%s/address", iface->interface_name);
    int fd;
    fd = open(arquivo, O_RDONLY, 0);
    char buf[100];
    read(fd, buf, sizeof (buf));
    buf[strlen(buf) - 1] = '\0';
    strcpy(iface->interface_mac_addr, buf);
    close(fd);
    return GET_MAC_ADDR_SUCCESS;
}

The error happends at "}", the last line of code.

I try to debug with GDB, but I'm new at this, so I do not understand many things that GDB tells me. Below is the output from GDB:

Core was generated by `./vfirewall-monitor'.
Program terminated with signal 6, Aborted.
#0  0x00007f36c043b425 in __GI_raise (sig=<optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
64  ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007f36c043b425 in __GI_raise (sig=<optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x00007f36c043eb8b in __GI_abort () at abort.c:91
#2  0x00007f36c047939e in __libc_message (do_abort=2, fmt=0x7f36c058157f "*** %s ***: %s terminated\n")
    at ../sysdeps/unix/sysv/linux/libc_fatal.c:201
#3  0x00007f36c050ff47 in __GI___fortify_fail (msg=0x7f36c0581567 "stack smashing detected") at fortify_fail.c:32
#4  0x00007f36c050ff10 in __stack_chk_fail () at stack_chk_fail.c:29
#5  0x00000000004029be in get_interface_mac_addr (iface=0x7f36b4004560) at interfaces.c:340
#6  0x00000000004022c9 in get_interfaces_info (iface=0x7f36b4004560) at interfaces.c:87
#7  0x0000000000402d9d in get_all_system_info () at kernel.c:109
#8  0x00007f36c07cce9a in start_thread (arg=0x7f36bb729700) at pthread_create.c:308
#9  0x00007f36c04f93fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#10 0x0000000000000000 in ?? ()
(gdb)

Someone know whats going on in this case? I do something wrong and a can see what is?

many thanks.

Answer 1

char arquivo[10]; // <-- here
sprintf(arquivo, "/sys/class/net/%s/address", iface->interface_name);

arquivo is way too small for that string.

You should also check the return value of open():

fd = open(arquivo, O_RDONLY, 0);
if(fd < 0) {
    perror("open");
    // do something
}

This also wrong:

read(fd, buf, sizeof (buf));
buf[strlen(buf) - 1] = '\0';
    ^^^^^^^^^^^

read() does not null terminate anything. You can't call strlen() on buf. Instead:

int n = read(fd, buf, sizeof (buf));
if(n < 0) {
    perror("read");
    // do something
}
buf[n] = '\0';