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Date: Tue, 30 Aug 2022 18:03:31 +0800
From: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>,
Saravana Kannan <saravanak@...gle.com>
CC: <linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <patches@...linux.org.uk>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
"Linus Walleij" <linus.walleij@...aro.org>
Subject: Re: [PATCH v2] ARM: Add sanity check for dev->periphid in
amba_probe()
On 2022/8/30 17:47, Russell King (Oracle) wrote:
> On Tue, Aug 30, 2022 at 12:20:00AM -0700, Saravana Kannan wrote:
>> On Mon, Aug 29, 2022 at 11:59 PM Zhen Lei <thunder.leizhen@...wei.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@...wei.com>
>>> ---
>>> KernelVersion: v6.0-rc3
>>> drivers/amba/bus.c | 24 +++++++++++++++++++++---
>>> 1 file changed, 21 insertions(+), 3 deletions(-)
>>>
>>> v1 --> v2:
>>> 1. Update this patch based on:
>>> https://lore.kernel.org/lkml/20220818172852.3548-1-isaacmanjarres@google.com/
>>> 2. Move the operations of sanity checking and reading dev->periphid,
>>> updating uevent into new function amba_prepare_periphid().
>>>
>>> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
>>> index 110a535648d2e1f..8e4c7e190880206 100644
>>> --- a/drivers/amba/bus.c
>>> +++ b/drivers/amba/bus.c
>>> @@ -204,10 +204,9 @@ static int amba_read_periphid(struct amba_device *dev)
>>> return ret;
>>> }
>>>
>>> -static int amba_match(struct device *dev, struct device_driver *drv)
>>> +static int amba_prepare_periphid(struct device *dev)
>>> {
>>> struct amba_device *pcdev = to_amba_device(dev);
>>> - struct amba_driver *pcdrv = to_amba_driver(drv);
>>>
>>> mutex_lock(&pcdev->periphid_lock);
>>> if (!pcdev->periphid) {
>>> @@ -228,6 +227,19 @@ static int amba_match(struct device *dev, struct device_driver *drv)
>>> }
>>> mutex_unlock(&pcdev->periphid_lock);
>>>
>>> + return 0;
>>> +}
>>> +
>>> +static int amba_match(struct device *dev, struct device_driver *drv)
>>> +{
>>> + struct amba_device *pcdev = to_amba_device(dev);
>>> + struct amba_driver *pcdrv = to_amba_driver(drv);
>>> + int ret;
>>> +
>>> + ret = amba_prepare_periphid(dev);
>>> + if (ret)
>>> + return ret;
>>> +
>>> /* When driver_override is set, only bind to the matching driver */
>>> if (pcdev->driver_override)
>>> return !strcmp(pcdev->driver_override, drv->name);
>>> @@ -278,9 +290,15 @@ 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;
>>>
>>> + ret = amba_prepare_periphid(dev);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + id = amba_lookup(pcdrv->id_table, pcdev);
>>> +
>>> do {
>>> ret = of_amba_device_decode_irq(pcdev);
>>> if (ret)
>>
>> Let's wait for Isaac to review this. He has been looking at the
>> locking issue for a bit and there were some tricky cases.
>
> How can we get to amba_probe() if amba_match() has not returned a
> positive match for an ID? Surely if that happens, the driver model
Always return true.
__driver_attach
driver_match_device
static inline int driver_match_device(struct device_driver *drv,
struct device *dev)
{
return drv->bus->match ? drv->bus->match(dev, drv) : 1;
}
> is failed - since a probe function should not be called unless the
> driver matches the device.
>
> This patch, and 9229/1 both feel like they're working around some
> brokenness elsewhere in the kernel.
>
> The description in 9229/1, specifically "But not all drivers have .match
> hook, such as pl031, the dev->bus->probe will be called directly in
> __driver_attach()." AMBA drivers do not have a .match hook - the bus
> does, which all AMBA drivers must be a member of. If amba_match fails,
> there is no way that amba_probe() should ever be called.
>
--
Regards,
Zhen Lei
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