Messages in this thread | | | Date | Tue, 30 Aug 2022 11:07:56 +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 06:03:31PM +0800, Leizhen (ThunderTown) wrote: > > > 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@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 > > 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; > }
You seem to be misunderstanding something rather fundamental here.
For an amba driver, drv->bus will always be pointing at amba_bustype. That always has a "match" operation. Therefore, the default of '1' above will *never* be used for an AMBA driver.
If drv->bus does not point at amba_bustype, then amba_probe() will not be called for "drv".
Therefore, amba_match() must always be called before amba_probe().
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