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SubjectRe: [PATCH] ARM: 9220/1: amba: Add sanity check for dev->periphid in amba_probe()
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On 2022/8/30 5:17, Saravana Kannan wrote:
> On Sat, Aug 27, 2022 at 3:21 AM Zhen Lei <thunder.leizhen@huawei.com> wrote:
>>
>> Commit f2d3b9a46e0e ("ARM: 9220/1: amba: Remove deferred device addition")
>> forcibly invokes device_add() even if dev->periphid is not ready. Although
>> it will be remedied in amba_match(): dev->periphid will be initialized
>> if everything is in place; Otherwise, return -EPROBE_DEFER to block
>> __driver_attach() from further execution. But not all drivers have .match
>> hook, such as pl031, the dev->bus->probe will be called directly in
>> __driver_attach(). Unfortunately, if dev->periphid is still not
>> initialized, the following exception will be triggered.
>>
>> 8<--- cut here ---
>> Unable to handle kernel NULL pointer dereference at virtual address 00000008
>> [00000008] *pgd=00000000
>> Internal error: Oops: 5 [#1] SMP ARM
>> Modules linked in:
>> CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.0.0-rc2+ #7
>> Hardware name: ARM-Versatile Express
>> PC is at pl031_probe+0x8/0x208
>> LR is at amba_probe+0xf0/0x160
>> pc : 80698df8 lr : 8050eb54 psr: 80000013
>> sp : c0825df8 ip : 00000000 fp : 811fda38
>> r10: 00000000 r9 : 80d72470 r8 : fffffdfb
>> r7 : 811fd800 r6 : be7eb330 r5 : 00000000 r4 : 811fd900
>> r3 : 80698df0 r2 : 37000000 r1 : 00000000 r0 : 811fd800
>> Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
>> Control: 10c5387d Table: 6000406a DAC: 00000051
>> ... ...
>> pl031_probe from amba_probe+0xf0/0x160
>> amba_probe from really_probe+0x118/0x290
>> really_probe from __driver_probe_device+0x84/0xe4
>> __driver_probe_device from driver_probe_device+0x30/0xd0
>> driver_probe_device from __driver_attach+0x8c/0xfc
>> __driver_attach from bus_for_each_dev+0x70/0xb0
>> bus_for_each_dev from bus_add_driver+0x168/0x1f4
>> bus_add_driver from driver_register+0x7c/0x118
>> driver_register from do_one_initcall+0x44/0x1ec
>> do_one_initcall from kernel_init_freeable+0x238/0x288
>> kernel_init_freeable from kernel_init+0x18/0x12c
>> kernel_init from ret_from_fork+0x14/0x2c
>> ... ...
>> ---[ end trace 0000000000000000 ]---
>>
>> Therefore, take the same action as in amba_match(): return -EPROBE_DEFER
>> if dev->periphid is not ready in amba_probe().
>>
>> Fixes: f2d3b9a46e0e ("ARM: 9220/1: amba: Remove deferred device addition")
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>> KernelVersion: v6.0-rc2
>> drivers/amba/bus.c | 10 +++++++++-
>> 1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
>> index 32b0e0b930c1068..2e5572f60692a33 100644
>> --- a/drivers/amba/bus.c
>> +++ b/drivers/amba/bus.c
>> @@ -274,9 +274,17 @@ static int amba_probe(struct device *dev)
>> {
>> struct amba_device *pcdev = to_amba_device(dev);
>> struct amba_driver *pcdrv = to_amba_driver(dev->driver);
>> - const struct amba_id *id = amba_lookup(pcdrv->id_table, pcdev);
>> + const struct amba_id *id;
>> int ret;
>>
>> + if (!pcdev->periphid) {
>> + ret = amba_read_periphid(pcdev);
>> + if (ret)
>> + return -EPROBE_DEFER;
>> + }
>> +
>> + id = amba_lookup(pcdrv->id_table, pcdev);
>> +
>> do {
>> ret = of_amba_device_decode_irq(pcdev);
>> if (ret)
>
> Cc: Isaac
>
> Hi Zhen,
>
> Thanks for the report and trying to fix it. I think your change is in
> the right direction but there are a couple of issues that need to be
> addressed.
>
> Firstly, please make your change on top of [1] that fixes a race in my
> patch. So, you'll need to use some locks here. Also, you'll need to do
> the uevent update thing I do in amba_match() when you read the
> periphid successfully for the first time.

OK, I will do it in v2. It seems necessary to add a helper function to
avoid duplication of code.

>
> Thanks,
> Saravana
>
> [1] - https://lore.kernel.org/lkml/20220818172852.3548-1-isaacmanjarres@google.com/
> .
>

--
Regards,
Zhen Lei

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