Messages in this thread Patch in this message | | | From | Alexandre Belloni <> | Subject | [PATCH] uio: ensure class is registered before devices | Date | Fri, 15 Jun 2018 17:52:49 +0200 |
| |
When both uio and the uio drivers are built in the kernel, it is possible for a driver to register devices before the uio class is registered.
This may result in a NULL pointer dereference later on in get_device_parent() when accessing the class glue_dirs spinlock.
The trace looks like that:
Unable to handle kernel NULL pointer dereference at virtual address 00000140 [...] Process swapper/0 (pid: 1, stack limit = 0xffff000008070000) Call trace: Exception stack(0xffff000008073810 to 0xffff000008073950) 3800: 0000000000000140 0000000000000001 3820: ffff800078f60000 ffffffffffffffff 0000000000000000 0000000000000000 3840: 0000000000000d39 07650764075f0774 0765076307690776 077207610770075f 3860: 07200774076e0765 0720072007200720 0720072007200720 0720072007200720 3880: 0720072007200720 ffffffffffffffff 0000000000000000 ffff0000089e88c0 38a0: 0000000000000010 ffff000008e0c000 ffff8000780990b0 ffff8000780f4ec0 38c0: ffff000008c41a48 ffff000008c41a30 ffff000008a59660 ffff000008c41a30 38e0: ffff000008a59660 ffff8000780f4c80 ffff000008c41000 ffff000008073950 3900: ffff0000084f3bb0 ffff000008073950 ffff0000089cc234 0000000040000045 3920: 00000000000005e7 ffff000008a59660 ffffffffffffffff 0000000000000000 3940: ffff000008073950 ffff0000089cc234 [<ffff0000089cc234>] _raw_spin_lock+0x14/0x48 [<ffff0000084f56bc>] device_add+0x154/0x6a0 [<ffff0000084f5e48>] device_create_groups_vargs+0x120/0x128 [<ffff0000084f5edc>] device_create+0x54/0x60 [<ffff0000086e72c0>] __uio_register_device+0x120/0x4a8 [<ffff000008528b7c>] jaguar2_pci_probe+0x2d4/0x558 [<ffff0000083fc18c>] local_pci_probe+0x3c/0xb8 [<ffff0000083fd81c>] pci_device_probe+0x11c/0x180 [<ffff0000084f88bc>] driver_probe_device+0x22c/0x2d8 [<ffff0000084f8a24>] __driver_attach+0xbc/0xc0 [<ffff0000084f69fc>] bus_for_each_dev+0x4c/0x98 [<ffff0000084f81b8>] driver_attach+0x20/0x28 [<ffff0000084f7d08>] bus_add_driver+0x1b8/0x228 [<ffff0000084f93c0>] driver_register+0x60/0xf8 [<ffff0000083fb918>] __pci_register_driver+0x40/0x48
Return EPROBE_DEFER in that case so the driver can register the device later.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> ---
Hi Greg,
I'm not sure using struct class::p to test for class registration is really something we should do but this allows to have a small patch.
The other solutions to fix this are: - use a similar change but with a boolean to store whether the class has been registered. - or instead of EPROBE_DEFER, just register the class when the first uio device is registered. _ or stop allowing to compile uio as a module and use subsys_initcall instead of module_init
What do you think?
drivers/uio/uio.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index e8f4ac9400ea..3fb84ab3dd99 100644 --- a/drivers/uio/uio.c +++ b/drivers/uio/uio.c @@ -853,6 +853,9 @@ int __uio_register_device(struct module *owner, struct uio_device *idev; int ret = 0; + if (!uio_class.p) + return -EPROBE_DEFER; + if (!parent || !info || !info->name || !info->version) return -EINVAL; -- 2.17.1
| |