On 2022/7/6 3:25, Saravana Kannan wrote: > On Fri, Sep 10, 2021 at 12:59 AM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote: >> >> >> On 2021/9/9 11:30, Saravana Kannan wrote: >>> On Fri, Aug 27, 2021 at 6:09 PM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote: >>>> >>>> On 2021/8/28 3:09, Saravana Kannan wrote: >>>>> On Fri, Aug 27, 2021 at 7:38 AM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote: >>>>>> On 2021/8/27 8:04, Saravana Kannan wrote: >>>>>>> On Thu, Aug 26, 2021 at 1:22 AM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote: >>>>>>>>>>> Btw, I've been working on [1] cleaning up the one-off deferred probe >>>>>>>>>>> solution that we have for amba devices. That causes a bunch of other >>>>>>>>>>> headaches. Your patch 3/3 takes us further in the wrong direction by >>>>>>>>>>> adding more reasons for delaying the addition of the device. >>>>>>>> Hi Saravana, I try the link[1], but with it, there is a crash when boot >>>>>>>> (qemu-system-arm -M vexpress-a15), >>>>> I'm assuming it's this one? >>>>> arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts >>>> I use arch/arm/boot/dts/vexpress-v2p-ca15-tc1.dts. >>>> >>>> qemu-system-arm -M vexpress-a15 -dtb vexpress-v2p-ca15-tc1.dtb -cpu >>>> cortex-a15 -smp 2 -m size=3G -kernel zImage -rtc base=localtime -initrd >>>> initrd-arm32 -append 'console=ttyAMA0 cma=0 kfence.sample_interval=0 >>>> earlyprintk debug ' -device virtio-net-device,netdev=net8 -netdev >>>> type=tap,id=net8,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown >>>> -nographic >>>> >>>>>>> Hi, >>>>>>> >>>>>>> It's hard to make sense of the logs. Looks like two different threads >>>>>>> might be printing to the log at the same time? Can you please enable >>>>>>> the config that prints the thread ID (forgot what it's called) and >>>>>>> collect this again? With what I could tell the crash seems to be >>>>>>> happening somewhere in platform_match(), but that's not related to >>>>>>> this patch at all? >>>>>> Can you reproduce it? it is very likely related(without your patch, the >>>>>> boot is fine), >>>>> Sorry, I haven't ever setup qemu and booted vexpress. Thanks for your help. >>>>> >>>>>> the NULL ptr is about serio, it is registed from amba driver. >>>>>> >>>>>> ambakmi_driver_init >>>>>> >>>>>> -- amba_kmi_probe >>>>>> >>>>>> -- __serio_register_port >>>>> Thanks for the pointer. I took a look at the logs and the code. It's >>>>> very strange. As you can see from the backtrace, platform_match() is >>>>> being called for the device_add() from serio_handle_event(). But the >>>>> device that gets added there is on the serio_bus which obviously >>>>> should be using the serio_bus_match. >>>> Yes, I am confused too. >>>>>> +Dmitry and input maillist, is there some known issue about serio ? >>>>>> >>>>>> I add some debug, the full log is attached. >>>>>> >>>>>> [ 2.958355][ T41] input: AT Raw Set 2 keyboard as >>>>>> /devices/platform/bus@8000000/bus@8000000:motherboard-bus/bus@8000000:motherboard-bus:iofpga-bus@300000000/1c060000.kmi/serio0/input/input0 >>>>>> [ 2.977441][ T41] serio serio1: pdev c1e05508, pdev->name (null), >>>>>> drv c1090fc0, drv->name vexpress-reset >>>>> Based on the logs you added, it's pretty clear we are getting to >>>>> platform_match(). It's also strange that the drv->name is >>>>> vexpress-reset >>>> ... >>>>>> [ 3.003113][ T41] Backtrace: >>>>>> [ 3.003451][ T41] [<c0560bb4>] (strcmp) from [<c0646358>] (platform_match+0xdc/0xf0) >>>>>> [ 3.003963][ T41] [<c064627c>] (platform_match) from [<c06437d4>] (__device_attach_driver+0x3c/0xf4) >>>>>> [ 3.004769][ T41] [<c0643798>] (__device_attach_driver) from [<c0641180>] (bus_for_each_drv+0x68/0xc8) >>>>>> [ 3.005481][ T41] [<c0641118>] (bus_for_each_drv) from [<c0642f40>] (__device_attach+0xf0/0x16c) >>>>>> [ 3.006152][ T41] [<c0642e50>] (__device_attach) from [<c06439d4>] (device_initial_probe+0x1c/0x20) >>>>>> [ 3.006853][ T41] [<c06439b8>] (device_initial_probe) from [<c0642030>] (bus_probe_device+0x94/0x9c) >>>>>> [ 3.007259][ T41] [<c0641f9c>] (bus_probe_device) from [<c063f9cc>] (device_add+0x408/0x8b8) >>>>>> [ 3.007900][ T41] [<c063f5c4>] (device_add) from [<c071c1cc>] (serio_handle_event+0x1b8/0x234) >>>>>> [ 3.008824][ T41] [<c071c014>] (serio_handle_event) from [<c01475a4>] (process_one_work+0x238/0x594) >>>>>> [ 3.009737][ T41] [<c014736c>] (process_one_work) from [<c014795c>] (worker_thread+0x5c/0x5f4) >>>>>> [ 3.010638][ T41] [<c0147900>] (worker_thread) from [<c014feb4>] (kthread+0x178/0x194) >>>>>> [ 3.011496][ T41] [<c014fd3c>] (kthread) from [<c0100150>] (ret_from_fork+0x14/0x24) >>>>>> [ 3.011860][ T41] Exception stack(0xc1675fb0 to 0xc1675ff8) >>>>> But the platform_match() is happening for the device_add() from >>>>> serio_event_handle() that's adding a device to the serio_bus and it >>>>> should be using serio_bus_match(). >>>>> >>>>> I haven't reached any conclusion yet, but my current thought process >>>>> is that it's either: >>>>> 1. My patch is somehow causing list corruption. But I don't directly >>>>> touch any list in my change (other than deleting a list entirely), so >>>>> it's not clear how that would be happening. >>>> Maybe some concurrent driver load？ >>>> >>>>> 2. Without my patch, these AMBA device's probe would be delayed at >>>>> least until 5 seconds or possibly later. I'm wondering if my patch is >>>>> catching some bad timing assumptions in other code. >>>> After Rob's patch, It will retry soon. >>>> >>>> commit 039599c92d3b2e73689e8b6e519d653fd4770abb >>>> Author: Rob Herring <robh@xxxxxxxxxx> >>>> Date: Wed Apr 29 15:58:12 2020 -0500 >>>> >>>> amba: Retry adding deferred devices at late_initcall >>>> >>>> If amba bus devices defer when adding, the amba bus code simply retries >>>> adding the devices every 5 seconds. This doesn't work well as it >>>> completely unsynchronized with starting the init process which can >>>> happen in less than 5 secs. Add a retry during late_initcall. If the >>>> amba devices are added, then deferred probe takes over. If the >>>> dependencies have not probed at this point, then there's no improvement >>>> over previous behavior. To completely solve this, we'd need to retry >>>> after every successful probe as deferred probe does. >>>> >>>> The list_empty() check now happens outside the mutex, but the mutex >>>> wasn't necessary in the first place. >>>> >>>> This needed to use deferred probe instead of fragile initcall ordering >>>> on 32-bit VExpress systems where the apb_pclk has a number of probe >>>> dependencies (vexpress-sysregs, vexpress-config). >>>> >>>> >>>>> You might be able to test out theory (2) by DEFERRED_DEVICE_TIMEOUT to >>>>> a much smaller number. Say 500ms or 100ms. If it doesn't crash, it >>>>> doesn't mean it's not (2), but if it does, then we know for sure it's >>>>> (2). >>>> ok, I will try this one, but due to above patch, it may not work. >>> Were you able to find anything more? >> I can't find any clue， and have no time to check this for now, is there >> any news from your side? Hi, Saravana and Kefeng: I've spent the whole afternoon trying to figure this out, and the fix patch has been cc you two. > > To close out this thread, the issue was due to a UAF bug in driver > core that was fixed by: > https://lore.kernel.org/all/20220513112444.45112-1-schspa@xxxxxxxxx/ > > With that fix, there wouldn't have been a crash, but amba driver > registration would have failed (because match returned > non-EPROBE_DEFER error). > > -Saravana > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- Regards, Zhen Lei
