[PATCH 4.4 36/38] netfilter: ipset: fix shift-out-of-bounds in htable_bits()

Greg Kroah-Hartman
2021-01-11T14:09:58Z

From: Vasily Averin <vvs@virtuozzo.com>

commit 5c8193f568ae16f3242abad6518dc2ca6c8eef86 upstream.

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.

Fixes: 1feab10d7e6d("netfilter: ipset: Unified hash type generation")
Reported-by: syzbot+d66bfadebca46cf61a2b@syzkaller.appspotmail.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/netfilter/ipset/ip_set_hash_gen.h | 20 +++++---------------
1 file changed, 5 insertions(+), 15 deletions(-)

--- a/net/netfilter/ipset/ip_set_hash_gen.h
+++ b/net/netfilter/ipset/ip_set_hash_gen.h
@@ -113,20 +113,6 @@ htable_size(u8 hbits)
return hsize * sizeof(struct hbucket *) + sizeof(struct htable);
}

-/* Compute htable_bits from the user input parameter hashsize */
-static u8
-htable_bits(u32 hashsize)
-{
- /* Assume that hashsize == 2^htable_bits */
- u8 bits = fls(hashsize - 1);
-
- if (jhash_size(bits) != hashsize)
- /* Round up to the first 2^n value */
- bits = fls(hashsize);
-
- return bits;
-}
-
#ifdef IP_SET_HASH_WITH_NETS
#if IPSET_NET_COUNT > 1
#define __CIDR(cidr, i) (cidr[i])
@@ -1309,7 +1295,11 @@ IPSET_TOKEN(HTYPE, _create)(struct net *
get_random_bytes(&h->initval, sizeof(h->initval));
set->timeout = IPSET_NO_TIMEOUT;

- hbits = htable_bits(hashsize);
+ /* Compute htable_bits from the user input parameter hashsize.
+ * Assume that hashsize == 2^htable_bits,
+ * otherwise round up to the first 2^n value.
+ */
+ hbits = fls(hashsize - 1);
hsize = htable_size(hbits);
if (hsize == 0) {
kfree(h);