bpf: fix a possible NULL deref in bpf_map_offload_map_alloc()

Call bpf_dev_offload_check() before netdev_lock_ops().

This is needed if attr->map_ifindex is not valid.

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000197: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000cb8-0x0000000000000cbf]
 RIP: 0010:netdev_need_ops_lock include/linux/netdevice.h:2792 [inline]
 RIP: 0010:netdev_lock_ops include/linux/netdevice.h:2803 [inline]
 RIP: 0010:bpf_map_offload_map_alloc+0x19a/0x910 kernel/bpf/offload.c:533
Call Trace:
 <TASK>
  map_create+0x946/0x11c0 kernel/bpf/syscall.c:1455
  __sys_bpf+0x6d3/0x820 kernel/bpf/syscall.c:5777
  __do_sys_bpf kernel/bpf/syscall.c:5902 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:5900 [inline]
  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5900
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83

Fixes: 97246d6d ("net: hold netdev instance lock during ndo_bpf")
Reported-by:  <syzbot+0c7bfd8cf3aecec92708@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/netdev/67caa2b1.050a0220.15b4b9.0077.GAE@google.com/T/#u


Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250307074303.1497911-1-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>