Messages in this thread | | | Date | Thu, 13 Apr 2023 16:11:30 +0800 | Subject | Re: [RFC PATCH net] sfc: Fix use-after-free due to selftest_work | From | Ding Hui <> |
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On 2023/4/13 15:52, Martin Habets wrote: > On Wed, Apr 12, 2023 at 03:34:51PM -0700, Jacob Keller wrote: >> >> >> On 4/11/2023 5:50 PM, 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(). >>> >>> [4] However, I also notice that in efx_ef10_set_mac_address(), the >>> efx_net_open() depends on original port_enabled, but others are not, >>> if we change all efx_net_open() depends on old state like >>> efx_ef10_set_mac_address() does, the UAF can also be fixed in theory. >>> >>> But I'm not sure which is better, is there any suggestions? Thanks. >>> >> >> I think this fix makes the most sense to me. > > For me this is too late. It leaves a gap where the selftest timer is still running > but the NIC has already stopped sending events. So we could still get a > failure "channel %d timed out waiting for event queue" from the selftest. >
Yes, assuming not consider removing, scheduled selftest_work if NIC not brought up actually, we will also get this failure log.
-- Thanks, - Ding Hui
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