[net] mptcp: Fix crash due to tcp_tsorted_anchor was initialized before release skb

Commit Message

Mat Martineau March 17, 2022, 10:09 p.m. UTC

From: Yonglong Li <[e-mail]>

Got crash when doing pressure test of mptcp:

===========================================================================
dst_release: dst:ffffa06ce6e5c058 refcnt:-1
kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
BUG: unable to handle kernel paging request at ffffa06ce6e5c058
PGD 190a01067 P4D 190a01067 PUD 43fffb067 PMD 22e403063 PTE 8000000226e5c063
Oops: 0011 [#1] SMP PTI
CPU: 7 PID: 7823 Comm: kworker/7:0 Kdump: loaded Tainted: G            E
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.2.1 04/01/2014
Call Trace:
 ? skb_release_head_state+0x68/0x100
 ? skb_release_all+0xe/0x30
 ? kfree_skb+0x32/0xa0
 ? mptcp_sendmsg_frag+0x57e/0x750
 ? __mptcp_retrans+0x21b/0x3c0
 ? __switch_to_asm+0x35/0x70
 ? mptcp_worker+0x25e/0x320
 ? process_one_work+0x1a7/0x360
 ? worker_thread+0x30/0x390
 ? create_worker+0x1a0/0x1a0
 ? kthread+0x112/0x130
 ? kthread_flush_work_fn+0x10/0x10
 ? ret_from_fork+0x35/0x40
===========================================================================

In __mptcp_alloc_tx_skb skb was allocated and skb->tcp_tsorted_anchor will
be initialized, in under memory pressure situation sk_wmem_schedule will
return false and then kfree_skb. In this case skb->_skb_refdst is not null
because_skb_refdst and tcp_tsorted_anchor are stored in the same mem, and
kfree_skb will try to release dst and cause crash.

Fixes: f70cad1085d1 ("mptcp: stop relying on tcp_tx_skb_cache")
Cc: [e-mail]
Reviewed-by: Paolo Abeni <[e-mail]>
Signed-off-by: Yonglong Li <[e-mail]>
Signed-off-by: Mat Martineau <[e-mail]>
---
 net/mptcp/protocol.c | 1 +
 1 file changed, 1 insertion(+)


base-commit: 551acdc3c3d2b6bc97f11e31dcf960bc36343bfc

Comments

[e-mail] March 18, 2022, 9:20 p.m. UTC | #1

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <[e-mail]>:

On Thu, 17 Mar 2022 15:09:53 -0700 you wrote:
> From: Yonglong Li <[e-mail]>
> 
> Got crash when doing pressure test of mptcp:
> 
> ===========================================================================
> dst_release: dst:ffffa06ce6e5c058 refcnt:-1
> kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
> BUG: unable to handle kernel paging request at ffffa06ce6e5c058
> PGD 190a01067 P4D 190a01067 PUD 43fffb067 PMD 22e403063 PTE 8000000226e5c063
> Oops: 0011 [#1] SMP PTI
> CPU: 7 PID: 7823 Comm: kworker/7:0 Kdump: loaded Tainted: G            E
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.2.1 04/01/2014
> Call Trace:
>  ? skb_release_head_state+0x68/0x100
>  ? skb_release_all+0xe/0x30
>  ? kfree_skb+0x32/0xa0
>  ? mptcp_sendmsg_frag+0x57e/0x750
>  ? __mptcp_retrans+0x21b/0x3c0
>  ? __switch_to_asm+0x35/0x70
>  ? mptcp_worker+0x25e/0x320
>  ? process_one_work+0x1a7/0x360
>  ? worker_thread+0x30/0x390
>  ? create_worker+0x1a0/0x1a0
>  ? kthread+0x112/0x130
>  ? kthread_flush_work_fn+0x10/0x10
>  ? ret_from_fork+0x35/0x40
> ===========================================================================
> 
> [...]

Here is the summary with links:
  - [net] mptcp: Fix crash due to tcp_tsorted_anchor was initialized before release skb
    https://git.kernel.org/netdev/net/c/3ef3905aa3b5

You are awesome, thank you!

Patch

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 1c72f25f083e..014c9d88f947 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1196,6 +1196,7 @@  static struct sk_buff *__mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, g
 		tcp_skb_entail(ssk, skb);
 		return skb;
 	}
+	tcp_skb_tsorted_anchor_cleanup(skb);
 	kfree_skb(skb);
 	return NULL;
 }