4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ Upstream commit 92ceba94de6fb4cee2bf40b485979c342f44a492 ]
syzbot found that nf_dup_ipv4() or nf_dup_ipv6() could write per-cpu variable nf_skb_duplicated in an unsafe way [1].
Disabling preemption as hinted by the splat is not enough, we have to disable soft interrupts as well.
[1] BUG: using __this_cpu_write() in preemptible [00000000] code: syz.4.282/6316 caller is nf_dup_ipv4+0x651/0x8f0 net/ipv4/netfilter/nf_dup_ipv4.c:87 CPU: 0 UID: 0 PID: 6316 Comm: syz.4.282 Not tainted 6.11.0-rc7-syzkaller-00104-g7052622fccb1 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:93 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119 check_preemption_disabled+0x10e/0x120 lib/smp_processor_id.c:49 nf_dup_ipv4+0x651/0x8f0 net/ipv4/netfilter/nf_dup_ipv4.c:87 nft_dup_ipv4_eval+0x1db/0x300 net/ipv4/netfilter/nft_dup_ipv4.c:30 expr_call_ops_eval net/netfilter/nf_tables_core.c:240 [inline] nft_do_chain+0x4ad/0x1da0 net/netfilter/nf_tables_core.c:288 nft_do_chain_ipv4+0x202/0x320 net/netfilter/nft_chain_filter.c:23 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline] nf_hook_slow+0xc3/0x220 net/netfilter/core.c:626 nf_hook+0x2c4/0x450 include/linux/netfilter.h:269 NF_HOOK_COND include/linux/netfilter.h:302 [inline] ip_output+0x185/0x230 net/ipv4/ip_output.c:433 ip_local_out net/ipv4/ip_output.c:129 [inline] ip_send_skb+0x74/0x100 net/ipv4/ip_output.c:1495 udp_send_skb+0xacf/0x1650 net/ipv4/udp.c:981 udp_sendmsg+0x1c21/0x2a60 net/ipv4/udp.c:1269 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x1a6/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597 ___sys_sendmsg net/socket.c:2651 [inline] __sys_sendmmsg+0x3b2/0x740 net/socket.c:2737 __do_sys_sendmmsg net/socket.c:2766 [inline] __se_sys_sendmmsg net/socket.c:2763 [inline] __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2763 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f4ce4f7def9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f4ce5d4a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f4ce5135f80 RCX: 00007f4ce4f7def9 RDX: 0000000000000001 RSI: 0000000020005d40 RDI: 0000000000000006 RBP: 00007f4ce4ff0b76 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f4ce5135f80 R15: 00007ffd4cbc6d68 </TASK>
Fixes: d877f07112f1 ("netfilter: nf_tables: add nft_dup expression") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/netfilter/nf_dup_ipv4.c | 7 +++++-- net/ipv6/netfilter/nf_dup_ipv6.c | 7 +++++-- 2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/netfilter/nf_dup_ipv4.c b/net/ipv4/netfilter/nf_dup_ipv4.c index 39895b9ddeb96..b385c97ddc29b 100644 --- a/net/ipv4/netfilter/nf_dup_ipv4.c +++ b/net/ipv4/netfilter/nf_dup_ipv4.c @@ -55,8 +55,9 @@ void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum, { struct iphdr *iph;
+ local_bh_disable(); if (this_cpu_read(nf_skb_duplicated)) - return; + goto out; /* * Copy the skb, and route the copy. Will later return %XT_CONTINUE for * the original skb, which should continue on its way as if nothing has @@ -64,7 +65,7 @@ void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum, */ skb = pskb_copy(skb, GFP_ATOMIC); if (skb == NULL) - return; + goto out;
#if IS_ENABLED(CONFIG_NF_CONNTRACK) /* Avoid counting cloned packets towards the original connection. */ @@ -93,6 +94,8 @@ void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum, } else { kfree_skb(skb); } +out: + local_bh_enable(); } EXPORT_SYMBOL_GPL(nf_dup_ipv4);
diff --git a/net/ipv6/netfilter/nf_dup_ipv6.c b/net/ipv6/netfilter/nf_dup_ipv6.c index 4a7ddeddbaabf..941e389c227f3 100644 --- a/net/ipv6/netfilter/nf_dup_ipv6.c +++ b/net/ipv6/netfilter/nf_dup_ipv6.c @@ -50,11 +50,12 @@ static bool nf_dup_ipv6_route(struct net *net, struct sk_buff *skb, void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum, const struct in6_addr *gw, int oif) { + local_bh_disable(); if (this_cpu_read(nf_skb_duplicated)) - return; + goto out; skb = pskb_copy(skb, GFP_ATOMIC); if (skb == NULL) - return; + goto out;
#if IS_ENABLED(CONFIG_NF_CONNTRACK) nf_reset(skb); @@ -72,6 +73,8 @@ void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum, } else { kfree_skb(skb); } +out: + local_bh_enable(); } EXPORT_SYMBOL_GPL(nf_dup_ipv6);