[PATCH] avoid buffer overflow in sunrpc clnt_create (BZ #22542)

[Paul Eggert]

On 02/07/2018 01:25 PM, Dmitry V. Levin wrote:
> If strncpy starts generating a compilation error,  > then the only available choice seems to be memcpy:
Yes, memcpy is typically the way to go here.

> 	len = strlen(av[1]);  > assert(len > 0 && len <= sizeof(addr.sun_path)); > > if (++len > 
sizeof(addr.sun_path)) > len = sizeof(addr.sun_path); > > 
memcpy(addr.sun_path, av[1], len); > len += offsetof(struct sockaddr_un, 
sun_path); > > unlink(av[1]);
Yes, that should also work and it'll fix the unlink bug that I 
mentioned. You might also want to replace the "if" statement with "len 
+= len < sizeof(addr.sun_path);", as that's simpler.

> As struct sockaddr_un.sun_path is not necessarily a C string, pretending  > that it is a C string would encourage users to replace strncpy with 
 > memcpy.
There's nothing wrong with using memcpy for this test. On the contrary, 
memcpy improves the test by not unnecessarily initializing the part of 
addr.sun_path that doesn't need initializing. Programs like valgrind can 
use this information to catch bugs that the strncpy version would mask.