[net,1/2] netfilter: nf_tables: avoid overflows in nft_hash_buckets()

Message ID 20210506125323.3887186-1-eric.dumazet@gmail.com
State New
Headers show
Series
  • [net,1/2] netfilter: nf_tables: avoid overflows in nft_hash_buckets()
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Commit Message

Eric Dumazet May 6, 2021, 12:53 p.m.
From: Eric Dumazet <edumazet@google.com>

Number of buckets being stored in 32bit variables, we have to
ensure that no overflows occur in nft_hash_buckets()

syzbot injected a size == 0x40000000 and reported:

UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13
shift exponent 64 is too large for 64-bit type 'long unsigned int'
CPU: 1 PID: 29539 Comm: syz-executor.4 Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 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:327
 __roundup_pow_of_two include/linux/log2.h:57 [inline]
 nft_hash_buckets net/netfilter/nft_set_hash.c:411 [inline]
 nft_hash_estimate.cold+0x19/0x1e net/netfilter/nft_set_hash.c:652
 nft_select_set_ops net/netfilter/nf_tables_api.c:3586 [inline]
 nf_tables_newset+0xe62/0x3110 net/netfilter/nf_tables_api.c:4322
 nfnetlink_rcv_batch+0xa09/0x24b0 net/netfilter/nfnetlink.c:488
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:612 [inline]
 nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:630
 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46

Fixes: 0ed6389c483d ("netfilter: nf_tables: rename set implementations")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
 net/netfilter/nft_set_hash.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Comments

Pablo Neira Ayuso May 7, 2021, 7:59 a.m. | #1
On Thu, May 06, 2021 at 05:53:23AM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>

> 

> Number of buckets being stored in 32bit variables, we have to

> ensure that no overflows occur in nft_hash_buckets()

> 

> syzbot injected a size == 0x40000000 and reported:

> 

> UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13

> shift exponent 64 is too large for 64-bit type 'long unsigned int'

> CPU: 1 PID: 29539 Comm: syz-executor.4 Not tainted 5.12.0-rc7-syzkaller #0

> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

> Call Trace:

>  __dump_stack lib/dump_stack.c:79 [inline]

>  dump_stack+0x141/0x1d7 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:327

>  __roundup_pow_of_two include/linux/log2.h:57 [inline]

>  nft_hash_buckets net/netfilter/nft_set_hash.c:411 [inline]

>  nft_hash_estimate.cold+0x19/0x1e net/netfilter/nft_set_hash.c:652

>  nft_select_set_ops net/netfilter/nf_tables_api.c:3586 [inline]

>  nf_tables_newset+0xe62/0x3110 net/netfilter/nf_tables_api.c:4322

>  nfnetlink_rcv_batch+0xa09/0x24b0 net/netfilter/nfnetlink.c:488

>  nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:612 [inline]

>  nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:630

>  netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]

>  netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338

>  netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927

>  sock_sendmsg_nosec net/socket.c:654 [inline]

>  sock_sendmsg+0xcf/0x120 net/socket.c:674

>  ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350

>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2404

>  __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433

>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46


Applied, thanks.

Patch

diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c
index 58f576abcd4a7f22bb9d362550b98e79e2152af3..328f2ce32e4cbd772afe03a10f6d13a7ed6b93d5 100644
--- a/net/netfilter/nft_set_hash.c
+++ b/net/netfilter/nft_set_hash.c
@@ -412,9 +412,17 @@  static void nft_rhash_destroy(const struct nft_set *set)
 				    (void *)set);
 }
 
+/* Number of buckets is stored in u32, so cap our result to 1U<<31 */
+#define NFT_MAX_BUCKETS (1U << 31)
+
 static u32 nft_hash_buckets(u32 size)
 {
-	return roundup_pow_of_two(size * 4 / 3);
+	u64 val = div_u64((u64)size * 4, 3);
+
+	if (val >= NFT_MAX_BUCKETS)
+		return NFT_MAX_BUCKETS;
+
+	return roundup_pow_of_two(val);
 }
 
 static bool nft_rhash_estimate(const struct nft_set_desc *desc, u32 features,