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SubjectRe: [PATCH v2] ARM: Add sanity check for dev->periphid in amba_probe()
On Mon, Aug 29, 2022 at 11:59 PM 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-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.

-Saravana

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