From: Wang Liang wangliang74@huawei.com

commit 073d89808c065ac4c672c0a613a71b27a80691cb upstream.

Syzkaller reported this warning: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 16 at net/ipv4/af_inet.c:156 inet_sock_destruct+0x1c5/0x1e0 Modules linked in: CPU: 0 UID: 0 PID: 16 Comm: ksoftirqd/0 Not tainted 6.12.0-rc5 #26 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:inet_sock_destruct+0x1c5/0x1e0 Code: 24 12 4c 89 e2 5b 48 c7 c7 98 ec bb 82 41 5c e9 d1 18 17 ff 4c 89 e6 5b 48 c7 c7 d0 ec bb 82 41 5c e9 bf 18 17 ff 0f 0b eb 83 <0f> 0b eb 97 0f 0b eb 87 0f 0b e9 68 ff ff ff 66 66 2e 0f 1f 84 00 RSP: 0018:ffffc9000008bd90 EFLAGS: 00010206 RAX: 0000000000000300 RBX: ffff88810b172a90 RCX: 0000000000000007 RDX: 0000000000000002 RSI: 0000000000000300 RDI: ffff88810b172a00 RBP: ffff88810b172a00 R08: ffff888104273c00 R09: 0000000000100007 R10: 0000000000020000 R11: 0000000000000006 R12: ffff88810b172a00 R13: 0000000000000004 R14: 0000000000000000 R15: ffff888237c31f78 FS: 0000000000000000(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffc63fecac8 CR3: 000000000342e000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? __warn+0x88/0x130 ? inet_sock_destruct+0x1c5/0x1e0 ? report_bug+0x18e/0x1a0 ? handle_bug+0x53/0x90 ? exc_invalid_op+0x18/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? inet_sock_destruct+0x1c5/0x1e0 __sk_destruct+0x2a/0x200 rcu_do_batch+0x1aa/0x530 ? rcu_do_batch+0x13b/0x530 rcu_core+0x159/0x2f0 handle_softirqs+0xd3/0x2b0 ? __pfx_smpboot_thread_fn+0x10/0x10 run_ksoftirqd+0x25/0x30 smpboot_thread_fn+0xdd/0x1d0 kthread+0xd3/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x34/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> ---[ end trace 0000000000000000 ]---

Its possible that two threads call tcp_v6_do_rcv()/sk_forward_alloc_add() concurrently when sk->sk_state == TCP_LISTEN with sk->sk_lock unlocked, which triggers a data-race around sk->sk_forward_alloc: tcp_v6_rcv tcp_v6_do_rcv skb_clone_and_charge_r sk_rmem_schedule __sk_mem_schedule sk_forward_alloc_add() skb_set_owner_r sk_mem_charge sk_forward_alloc_add() __kfree_skb skb_release_all skb_release_head_state sock_rfree sk_mem_uncharge sk_forward_alloc_add() sk_mem_reclaim // set local var reclaimable __sk_mem_reclaim sk_forward_alloc_add()

In this syzkaller testcase, two threads call tcp_v6_do_rcv() with skb->truesize=768, the sk_forward_alloc changes like this: (cpu 1) | (cpu 2) | sk_forward_alloc ... | ... | 0 __sk_mem_schedule() | | +4096 = 4096 | __sk_mem_schedule() | +4096 = 8192 sk_mem_charge() | | -768 = 7424 | sk_mem_charge() | -768 = 6656 ... | ... | sk_mem_uncharge() | | +768 = 7424 reclaimable=7424 | | | sk_mem_uncharge() | +768 = 8192 | reclaimable=8192 | __sk_mem_reclaim() | | -4096 = 4096 | __sk_mem_reclaim() | -8192 = -4096 != 0

The skb_clone_and_charge_r() should not be called in tcp_v6_do_rcv() when sk->sk_state is TCP_LISTEN, it happens later in tcp_v6_syn_recv_sock(). Fix the same issue in dccp_v6_do_rcv().

Suggested-by: Eric Dumazet edumazet@google.com Reviewed-by: Eric Dumazet edumazet@google.com Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets") Signed-off-by: Wang Liang wangliang74@huawei.com Link: https://patch.msgid.link/20241107023405.889239-1-wangliang74@huawei.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Alva Lan alvalan9@foxmail.com --- v2: For I had sent the patch two times, I added v2 to the subject to distinguish it from the v1 version. --- net/dccp/ipv6.c | 2 +- net/ipv6/tcp_ipv6.c | 4 +--- 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c index d90bb941f2ad..8f5f56b1e5f8 100644 --- a/net/dccp/ipv6.c +++ b/net/dccp/ipv6.c @@ -615,7 +615,7 @@ static int dccp_v6_do_rcv(struct sock *sk, struct sk_buff *skb) by tcp. Feel free to propose better solution. --ANK (980728) */ - if (np->rxopt.all) + if (np->rxopt.all && sk->sk_state != DCCP_LISTEN) opt_skb = skb_clone_and_charge_r(skb, sk);

if (sk->sk_state == DCCP_OPEN) { /* Fast path */ diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 06b4acbfd314..0ccaa78f6ff3 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1463,7 +1463,7 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb) by tcp. Feel free to propose better solution. --ANK (980728) */ - if (np->rxopt.all) + if (np->rxopt.all && sk->sk_state != TCP_LISTEN) opt_skb = skb_clone_and_charge_r(skb, sk);

reason = SKB_DROP_REASON_NOT_SPECIFIED; @@ -1502,8 +1502,6 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb) if (nsk != sk) { if (tcp_child_process(sk, nsk, skb)) goto reset; - if (opt_skb) - __kfree_skb(opt_skb); return 0; } } else