Subject: Re: [PATCH net v2 1/1] ibmvnic: fix race between xmit and reset

From: [email-masked]
Date: Fri, 18 Mar 2022 13:30:10 +0000

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <[email-masked]>:

On Wed, 16 Mar 2022 18:12:31 -0700 you wrote:
> There is a race between reset and the transmit paths that can lead to
> ibmvnic_xmit() accessing an scrq after it has been freed in the reset
> path. It can result in a crash like:
> 
> 	Kernel attempted to read user page (0) - exploit attempt? (uid: 0)
> 	BUG: Kernel NULL pointer dereference on read at 0x00000000
> 	Faulting instruction address: 0xc0080000016189f8
> 	Oops: Kernel access of bad area, sig: 11 [#1]
> 	...
> 	NIP [c0080000016189f8] ibmvnic_xmit+0x60/0xb60 [ibmvnic]
> 	LR [c000000000c0046c] dev_hard_start_xmit+0x11c/0x280
> 	Call Trace:
> 	[c008000001618f08] ibmvnic_xmit+0x570/0xb60 [ibmvnic] (unreliable)
> 	[c000000000c0046c] dev_hard_start_xmit+0x11c/0x280
> 	[c000000000c9cfcc] sch_direct_xmit+0xec/0x330
> 	[c000000000bfe640] __dev_xmit_skb+0x3a0/0x9d0
> 	[c000000000c00ad4] __dev_queue_xmit+0x394/0x730
> 	[c008000002db813c] __bond_start_xmit+0x254/0x450 [bonding]
> 	[c008000002db8378] bond_start_xmit+0x40/0xc0 [bonding]
> 	[c000000000c0046c] dev_hard_start_xmit+0x11c/0x280
> 	[c000000000c00ca4] __dev_queue_xmit+0x564/0x730
> 	[c000000000cf97e0] neigh_hh_output+0xd0/0x180
> 	[c000000000cfa69c] ip_finish_output2+0x31c/0x5c0
> 	[c000000000cfd244] __ip_queue_xmit+0x194/0x4f0
> 	[c000000000d2a3c4] __tcp_transmit_skb+0x434/0x9b0
> 	[c000000000d2d1e0] __tcp_retransmit_skb+0x1d0/0x6a0
> 	[c000000000d2d984] tcp_retransmit_skb+0x34/0x130
> 	[c000000000d310e8] tcp_retransmit_timer+0x388/0x6d0
> 	[c000000000d315ec] tcp_write_timer_handler+0x1bc/0x330
> 	[c000000000d317bc] tcp_write_timer+0x5c/0x200
> 	[c000000000243270] call_timer_fn+0x50/0x1c0
> 	[c000000000243704] __run_timers.part.0+0x324/0x460
> 	[c000000000243894] run_timer_softirq+0x54/0xa0
> 	[c000000000ea713c] __do_softirq+0x15c/0x3e0
> 	[c000000000166258] __irq_exit_rcu+0x158/0x190
> 	[c000000000166420] irq_exit+0x20/0x40
> 	[c00000000002853c] timer_interrupt+0x14c/0x2b0
> 	[c000000000009a00] decrementer_common_virt+0x210/0x220
> 
> [...]

Here is the summary with links:
  - [net,v2,1/1] ibmvnic: fix race between xmit and reset
    https://git.kernel.org/netdev/net/c/4219196d1f66

You are awesome, thank you!
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