On Wed, Jan 22, 2025 at 07:35:21PM +0800, alvalan9@xxxxxxxxxxx wrote:
> From: Wang Liang <wangliang74@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
> Signed-off-by: Wang Liang <wangliang74@xxxxxxxxxx>
> Link: https://patch.msgid.link/20241107023405.889239-1-wangliang74@xxxxxxxxxx
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Alva Lan <alvalan9@xxxxxxxxxxx>
> ---
> v2: For I had sent the patch two times, I added v2 to the subject to distinguish it from the v1 version.
Does not apply to 6.1.y at all :(
