Re: [PATCH v2] netfilter: ipset: fix shift-out-of-bounds in htable_bits()

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Thu, Dec 17, 2020 at 05:53:18PM +0300, Vasily Averin wrote:
> htable_bits() can call jhash_size(32) and trigger shift-out-of-bounds
> 
> UBSAN: shift-out-of-bounds in net/netfilter/ipset/ip_set_hash_gen.h:151:6
> shift exponent 32 is too large for 32-bit type 'unsigned int'
> CPU: 0 PID: 8498 Comm: syz-executor519
>  Not tainted 5.10.0-rc7-next-20201208-syzkaller #0
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x107/0x163 lib/dump_stack.c:120
>  ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
>  __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:395
>  htable_bits net/netfilter/ipset/ip_set_hash_gen.h:151 [inline]
>  hash_mac_create.cold+0x58/0x9b net/netfilter/ipset/ip_set_hash_gen.h:1524
>  ip_set_create+0x610/0x1380 net/netfilter/ipset/ip_set_core.c:1115
>  nfnetlink_rcv_msg+0xecc/0x1180 net/netfilter/nfnetlink.c:252
>  netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
>  nfnetlink_rcv+0x1ac/0x420 net/netfilter/nfnetlink.c:600
>  netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
>  netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
>  netlink_sendmsg+0x907/0xe40 net/netlink/af_netlink.c:1919
>  sock_sendmsg_nosec net/socket.c:652 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:672
>  ____sys_sendmsg+0x6e8/0x810 net/socket.c:2345
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2399
>  __sys_sendmsg+0xe5/0x1b0 net/socket.c:2432
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> This patch replaces htable_bits() by simple fls(hashsize - 1) call:
> it alone returns valid nbits both for round and non-round hashsizes.
> It is normal to set any nbits here because it is validated inside
> following htable_size() call which returns 0 for nbits>31.

Applied, thanks.