4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alexandre Belloni alexandre.belloni@bootlin.com
[ Upstream commit ae61cf5b9913027c6953a79ed3894da4f47061bd ]
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 [...] [<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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/uio/uio.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/drivers/uio/uio.c +++ b/drivers/uio/uio.c @@ -249,6 +249,8 @@ static struct class uio_class = { .dev_groups = uio_groups, };
+bool uio_class_registered; + /* * device functions */ @@ -780,6 +782,9 @@ static int init_uio_class(void) printk(KERN_ERR "class_register failed for uio\n"); goto err_class_register; } + + uio_class_registered = true; + return 0;
err_class_register: @@ -790,6 +795,7 @@ exit:
static void release_uio_class(void) { + uio_class_registered = false; class_unregister(&uio_class); uio_major_cleanup(); } @@ -809,6 +815,9 @@ int __uio_register_device(struct module struct uio_device *idev; int ret = 0;
+ if (!uio_class_registered) + return -EPROBE_DEFER; + if (!parent || !info || !info->name || !info->version) return -EINVAL;