Messages in this thread | | | Subject | Re: [PATCH v2] ARM: Add sanity check for dev->periphid in amba_probe() | From | "Leizhen (ThunderTown)" <> | Date | Tue, 30 Aug 2022 18:03:31 +0800 |
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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; }
> 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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