KMSAN reports the following error in packet_bind_spkt():

==================================================================
BUG: KMSAN: use of unitialized memory
CPU: 0 PID: 1074 Comm: packet Not tainted 4.8.0-rc6+ #1891
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 0000000000000000 ffff88006b6dfc08 ffffffff82559ae8 ffff88006b6dfb48
 ffffffff818a7c91 ffffffff85b9c870 0000000000000092 ffffffff85b9c550
 0000000000000000 0000000000000092 00000000ec400911 0000000000000002
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff82559ae8>] dump_stack+0x238/0x290 lib/dump_stack.c:51
 [<ffffffff818a6626>] kmsan_report+0x276/0x2e0 mm/kmsan/kmsan.c:1003
 [<ffffffff818a783b>] __msan_warning+0x5b/0xb0 mm/kmsan/kmsan_instr.c:424
 [<     inline     >] strlen lib/string.c:484
 [<ffffffff8259b58d>] strlcpy+0x9d/0x200 lib/string.c:144
 [<ffffffff84b2eca4>] packet_bind_spkt+0x144/0x230 net/packet/af_packet.c:3132
 [<ffffffff84242e4d>] SYSC_bind+0x40d/0x5f0 net/socket.c:1370
 [<ffffffff84242a22>] SyS_bind+0x82/0xa0 net/socket.c:1356
 [<ffffffff8515991b>] entry_SYSCALL_64_fastpath+0x13/0x8f arch/x86/entry/entry_64.o:?
chained origin: 00000000eba00911
 [<ffffffff810bb787>] save_stack_trace+0x27/0x50 arch/x86/kernel/stacktrace.c:67
 [<     inline     >] kmsan_save_stack_with_flags mm/kmsan/kmsan.c:322
 [<     inline     >] kmsan_save_stack mm/kmsan/kmsan.c:334
 [<ffffffff818a59f8>] kmsan_internal_chain_origin+0x118/0x1e0 mm/kmsan/kmsan.c:527
 [<ffffffff818a7773>] __msan_set_alloca_origin4+0xc3/0x130 mm/kmsan/kmsan_instr.c:380
 [<ffffffff84242b69>] SYSC_bind+0x129/0x5f0 net/socket.c:1356
 [<ffffffff84242a22>] SyS_bind+0x82/0xa0 net/socket.c:1356
 [<ffffffff8515991b>] entry_SYSCALL_64_fastpath+0x13/0x8f arch/x86/entry/entry_64.o:?
origin description: ----address@SYSC_bind (origin=00000000eb400911)
==================================================================

, upon running the following program as root:

=====================================
#include <string.h>
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>

int main() {
  struct sockaddr addr;
  memset(&addr, 0xff, sizeof(addr));
  addr.sa_family = AF_PACKET;
  int fd = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ALL));
  bind(fd, &addr, sizeof(addr));
  return 0;
}
=====================================

What happens here is as follows.

First, the contents of |addr| (16 bytes) in the user program are copied into the |struct sockaddr_storage address| (128 bytes) by the bind() syscall implementation:

1356 SYSCALL_DEFINE3(bind, int, fd, struct sockaddr __user *, umyaddr, int, addrlen)
1357 {
1358         struct socket *sock;
1359         struct sockaddr_storage address;
1360         int err, fput_needed;
1361 
1362         sock = sockfd_lookup_light(fd, &err, &fput_needed);
1363         if (sock) {
1364                 err = move_addr_to_kernel(umyaddr, addrlen, &address);
1365                 if (err >= 0) {
1366                         err = security_socket_bind(sock,
1367                                                    (struct sockaddr *)&address,
1368                                                    addrlen);
1369                         if (!err)
1370                                 err = sock->ops->bind(sock,
1371                                                       (struct sockaddr *)
1372                                                       &address, addrlen);
1373                 }
1374                 fput_light(sock->file, fput_needed);
1375         }
1376         return err;
1377 }

Then security_socket_bind() is called, which doesn't modify the contents of |address|, after which |address| is passed to sock->ops->bind(), in our case packet_bind_spkt():

tatic int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
3121                             int addr_len)
3122 {
3123         struct sock *sk = sock->sk;
3124         char name[15];
3125 
3126         /*
3127          *      Check legality
3128          */
3129 
3130         if (addr_len != sizeof(struct sockaddr))
3131                 return -EINVAL;
3132         strlcpy(name, uaddr->sa_data, sizeof(name));
3133 
3134         return packet_do_bind(sk, name, 0, pkt_sk(sk)->num);
3135 }

Here the string in uaddr->sa_data isn't guaranteed to be null-terminated (in our case it is not),
yet strlcpy() is called on it.
Then strlcpy() calls strlen(uaddr->sa_data), which starts reading uninitialized memory till it
finds a zero or hits an unmapped page.