Messages in this thread | | | Date | Tue, 30 Aug 2022 10:47:31 +0100 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH v2] ARM: Add sanity check for dev->periphid in amba_probe() |
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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@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.
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 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.
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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