diff options
authorVladimir Zapolskiy <vladimir_zapolskiy@mentor.com>2016-10-31 21:46:24 +0200
committerWolfram Sang <wsa@the-dreams.de>2016-11-04 20:36:58 +0100
commit147b36d5b70c083cc76770c47d60b347e8eaf231 (patch)
parenta909d3e636995ba7c349e2ca5dbb528154d4ac30 (diff)
i2c: core: fix NULL pointer dereference under race condition
Race condition between registering an I2C device driver and deregistering an I2C adapter device which is assumed to manage that I2C device may lead to a NULL pointer dereference due to the uninitialized list head of driver clients. The root cause of the issue is that the I2C bus may know about the registered device driver and thus it is matched by bus_for_each_drv(), but the list of clients is not initialized and commonly it is NULL, because I2C device drivers define struct i2c_driver as static and clients field is expected to be initialized by I2C core: i2c_register_driver() i2c_del_adapter() driver_register() ... bus_add_driver() ... ... bus_for_each_drv(..., __process_removed_adapter) ... i2c_do_del_adapter() ... list_for_each_entry_safe(..., &driver->clients, ...) INIT_LIST_HEAD(&driver->clients); To solve the problem it is sufficient to do clients list head initialization before calling driver_register(). The problem was found while using an I2C device driver with a sluggish registration routine on a bus provided by a physically detachable I2C master controller, but practically the oops may be reproduced under the race between arbitraty I2C device driver registration and managing I2C bus device removal e.g. by unbinding the latter over sysfs: % echo 21a4000.i2c > /sys/bus/platform/drivers/imx-i2c/unbind Unable to handle kernel NULL pointer dereference at virtual address 00000000 Internal error: Oops: 17 [#1] SMP ARM CPU: 2 PID: 533 Comm: sh Not tainted 4.9.0-rc3+ #61 Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) task: e5ada400 task.stack: e4936000 PC is at i2c_do_del_adapter+0x20/0xcc LR is at __process_removed_adapter+0x14/0x1c Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 35bd004a DAC: 00000051 Process sh (pid: 533, stack limit = 0xe4936210) Stack: (0xe4937d28 to 0xe4938000) Backtrace: [<c0667be0>] (i2c_do_del_adapter) from [<c0667cc0>] (__process_removed_adapter+0x14/0x1c) [<c0667cac>] (__process_removed_adapter) from [<c0516998>] (bus_for_each_drv+0x6c/0xa0) [<c051692c>] (bus_for_each_drv) from [<c06685ec>] (i2c_del_adapter+0xbc/0x284) [<c0668530>] (i2c_del_adapter) from [<bf0110ec>] (i2c_imx_remove+0x44/0x164 [i2c_imx]) [<bf0110a8>] (i2c_imx_remove [i2c_imx]) from [<c051a838>] (platform_drv_remove+0x2c/0x44) [<c051a80c>] (platform_drv_remove) from [<c05183d8>] (__device_release_driver+0x90/0x12c) [<c0518348>] (__device_release_driver) from [<c051849c>] (device_release_driver+0x28/0x34) [<c0518474>] (device_release_driver) from [<c0517150>] (unbind_store+0x80/0x104) [<c05170d0>] (unbind_store) from [<c0516520>] (drv_attr_store+0x28/0x34) [<c05164f8>] (drv_attr_store) from [<c0298acc>] (sysfs_kf_write+0x50/0x54) [<c0298a7c>] (sysfs_kf_write) from [<c029801c>] (kernfs_fop_write+0x100/0x214) [<c0297f1c>] (kernfs_fop_write) from [<c0220130>] (__vfs_write+0x34/0x120) [<c02200fc>] (__vfs_write) from [<c0221088>] (vfs_write+0xa8/0x170) [<c0220fe0>] (vfs_write) from [<c0221e74>] (SyS_write+0x4c/0xa8) [<c0221e28>] (SyS_write) from [<c0108a20>] (ret_fast_syscall+0x0/0x1c) Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de> Cc: stable@kernel.org
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 1704fc84d647..b432b64e307a 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -2179,6 +2179,7 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
/* add the driver to the list of i2c drivers in the driver core */
driver->driver.owner = owner;
driver->driver.bus = &i2c_bus_type;
+ INIT_LIST_HEAD(&driver->clients);
/* When registration returns, the driver core
* will have called probe() for all matching-but-unbound devices.
@@ -2189,7 +2190,6 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
pr_debug("driver [%s] registered\n", driver->driver.name);
- INIT_LIST_HEAD(&driver->clients);
/* Walk the adapters that are already present */
i2c_for_each_dev(driver, __process_new_driver);