Messages in this thread | | | Date | Fri, 14 Apr 2023 19:03:41 +0800 | Subject | Re: [RFC PATCH net] sfc: Fix use-after-free due to selftest_work | From | Ding Hui <> |
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On 2023/4/14 17:44, Martin Habets wrote: > On Thu, Apr 13, 2023 at 04:35:08PM +0800, Ding Hui wrote: >> On 2023/4/13 15:37, Martin Habets wrote: >>> On Wed, Apr 12, 2023 at 08:50:13AM +0800, Ding Hui wrote: >>>> There is a use-after-free scenario that is: >>>> >>>> When netif_running() is false, user set mac address or vlan tag to VF, >>>> the xxx_set_vf_mac() or xxx_set_vf_vlan() will invoke efx_net_stop() >>>> and efx_net_open(), since netif_running() is false, the port will not >>>> start and keep port_enabled false, but selftest_worker is scheduled >>>> in efx_net_open(). >>>> >>>> If we remove the device before selftest_worker run, the efx is freed, >>>> then we will get a UAF in run_timer_softirq() like this: >>>> >>>> [ 1178.907941] ================================================================== >>>> [ 1178.907948] BUG: KASAN: use-after-free in run_timer_softirq+0xdea/0xe90 >>>> [ 1178.907950] Write of size 8 at addr ff11001f449cdc80 by task swapper/47/0 >>>> [ 1178.907950] >>>> [ 1178.907953] CPU: 47 PID: 0 Comm: swapper/47 Kdump: loaded Tainted: G O --------- -t - 4.18.0 #1 >>>> [ 1178.907954] Hardware name: SANGFOR X620G40/WI2HG-208T1061A, BIOS SPYH051032-U01 04/01/2022 >>>> [ 1178.907955] Call Trace: >>>> [ 1178.907956] <IRQ> >>>> [ 1178.907960] dump_stack+0x71/0xab >>>> [ 1178.907963] print_address_description+0x6b/0x290 >>>> [ 1178.907965] ? run_timer_softirq+0xdea/0xe90 >>>> [ 1178.907967] kasan_report+0x14a/0x2b0 >>>> [ 1178.907968] run_timer_softirq+0xdea/0xe90 >>>> [ 1178.907971] ? init_timer_key+0x170/0x170 >>>> [ 1178.907973] ? hrtimer_cancel+0x20/0x20 >>>> [ 1178.907976] ? sched_clock+0x5/0x10 >>>> [ 1178.907978] ? sched_clock_cpu+0x18/0x170 >>>> [ 1178.907981] __do_softirq+0x1c8/0x5fa >>>> [ 1178.907985] irq_exit+0x213/0x240 >>>> [ 1178.907987] smp_apic_timer_interrupt+0xd0/0x330 >>>> [ 1178.907989] apic_timer_interrupt+0xf/0x20 >>>> [ 1178.907990] </IRQ> >>>> [ 1178.907991] RIP: 0010:mwait_idle+0xae/0x370 >>>> >>>> I am thinking about several ways to fix the issue: >>>> >>>> [1] In this RFC, I cancel the selftest_worker unconditionally in >>>> efx_pci_remove(). >>>> >>>> [2] Add a test condition, only invoke efx_selftest_async_start() when >>>> efx->port_enabled is true in efx_net_open(). >>>> >>>> [3] Move invoking efx_selftest_async_start() from efx_net_open() to >>>> efx_start_all() or efx_start_port(), that matching cancel action in >>>> efx_stop_port(). >>> >>> I think moving this to efx_start_port() is best, as you say to match >>> the cancel in efx_stop_port(). >>> >> >> If moving to efx_start_port(), should we worry about that IRQ_TIMEOUT >> is still enough? > > 1 second is a long time for a machine running code, so it does not worry me. > >> I'm not sure if there is a long time waiting from starting of schedule >> selftest_work to the ending of efx_net_open(). > > I see your point. Looking at efx_start_all() there is the call to > efx_start_datapath() after the call to efx_net_open(), which takes a ^^^^^^^^^^^^ Do you mean efx_start_port()?
> relatively long time (well under 200ms though). > Logically it would be better to move efx_selftest_async_start() after this > call. What do you think?
Agree with you.
> The point here is that efx_start_all() calls efx_start_port() early, and > efx_stop_all() also calls efx_stop_port() early. The calling sequence is > correct but they are not the strict inverse of each other. >
Yeah, that is what I noticed monitor_work does. Then I'll move efx_selftest_async_start() into efx_start_all(), follows the monitor_work.
-- Thanks, - Ding Hui
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