[PATCH v2] Input: uinput: Avoid Object-Already-Free with a global lock
From: Mukesh Ojha
Date: Wed Apr 10 2019 - 03:59:53 EST
uinput_destroy_device() gets called from two places. In one place,
uinput_ioctl_handler() where it is protected under a lock
udev->mutex but there is no protection on udev device from freeing
inside uinput_release().
This can result in Object-Already-Free case where uinput parent
device already got freed while a child being inserted inside it.
That result in a double free case for parent while kernfs_put()
being done for child in a failure path of adding a node.
[ 160.093398] Call trace:
[ 160.093417] kernfs_get+0x64/0x88
[ 160.093438] kernfs_new_node+0x94/0xc8
[ 160.093450] kernfs_create_dir_ns+0x44/0xfc
[ 160.093463] sysfs_create_dir_ns+0xa8/0x130
[ 160.093479] kobject_add_internal+0x278/0x650
[ 160.093491] kobject_add_varg+0xe0/0x130
[ 160.093502] kobject_add+0x15c/0x1d0
[ 160.093518] device_add+0x2bc/0xde0
[ 160.093533] input_register_device+0x5f4/0xa0c
[ 160.093547] uinput_ioctl_handler+0x1184/0x2198
[ 160.093560] uinput_ioctl+0x38/0x48
[ 160.093573] vfs_ioctl+0x7c/0xb4
[ 160.093585] do_vfs_ioctl+0x9ec/0x2350
[ 160.093597] SyS_ioctl+0x6c/0xa4
[ 160.093610] el0_svc_naked+0x34/0x38
[ 160.093621] ---[ end trace bccf0093cda2c538 ]---
[ 160.099041] =============================================================================
[ 160.107459] BUG kernfs_node_cache (Tainted: G S W O ): Object already free
[ 160.115235] -----------------------------------------------------------------------------
[ 160.115235]
[ 160.125151] Disabling lock debugging due to kernel taint
[ 160.130626] INFO: Allocated in __kernfs_new_node+0x8c/0x3c0 age=11 cpu=2 pid=7098
[ 160.138314] kmem_cache_alloc+0x358/0x388
[ 160.142445] __kernfs_new_node+0x8c/0x3c0
[ 160.146590] kernfs_new_node+0x80/0xc8
[ 160.150462] kernfs_create_dir_ns+0x44/0xfc
[ 160.154777] sysfs_create_dir_ns+0xa8/0x130
[ 160.158416] CPU5: update max cpu_capacity 1024
[ 160.159085] kobject_add_internal+0x278/0x650
[ 160.163567] kobject_add_varg+0xe0/0x130
[ 160.167606] kobject_add+0x15c/0x1d0
[ 160.168452] CPU5: update max cpu_capacity 780
[ 160.171287] get_device_parent+0x2d0/0x34c
[ 160.175510] device_add+0x240/0xde0
[ 160.178371] CPU6: update max cpu_capacity 916
[ 160.179108] input_register_device+0x5f4/0xa0c
[ 160.183686] uinput_ioctl_handler+0x1184/0x2198
[ 160.188346] uinput_ioctl+0x38/0x48
[ 160.191941] vfs_ioctl+0x7c/0xb4
[ 160.195261] do_vfs_ioctl+0x9ec/0x2350
[ 160.199111] SyS_ioctl+0x6c/0xa4
[ 160.202436] INFO: Freed in kernfs_put+0x2c8/0x434 age=14 cpu=0 pid=7096
[ 160.209230] kernfs_put+0x2c8/0x434
[ 160.212825] kobject_del+0x50/0xcc
[ 160.216332] cleanup_glue_dir+0x124/0x16c
[ 160.220456] device_del+0x55c/0x5c8
[ 160.224047] __input_unregister_device+0x274/0x2a8
[ 160.228974] input_unregister_device+0x90/0xd0
[ 160.233553] uinput_destroy_device+0x15c/0x1dc
[ 160.238131] uinput_release+0x44/0x5c
[ 160.241898] __fput+0x1f4/0x4e4
[ 160.245127] ____fput+0x20/0x2c
[ 160.248358] task_work_run+0x9c/0x174
[ 160.252127] do_notify_resume+0x104/0x6bc
[ 160.256253] work_pending+0x8/0x14
[ 160.259751] INFO: Slab 0xffffffbf0215ff00 objects=33 used=11 fp=0xffffffc0857ffd08 flags=0x8101
[ 160.268693] INFO: Object 0xffffffc0857ffd08 @offset=15624 fp=0xffffffc0857fefb0
[ 160.268693]
[ 160.277721] Redzone ffffffc0857ffd00: bb bb bb bb bb bb bb bb ........
[ 160.286656] Object ffffffc0857ffd08: 00 00 00 00 01 00 00 80 58 a2 37 45 c1 ff ff ff ........X.7E....
[ 160.296207] Object ffffffc0857ffd18: ae 21 10 0b 90 ff ff ff 20 fd 7f 85 c0 ff ff ff .!...... .......
[ 160.305780] Object ffffffc0857ffd28: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 160.315342] Object ffffffc0857ffd38: 00 00 00 00 00 00 00 00 7d a3 25 69 00 00 00 00 ........}.%i....
[ 160.324896] Object ffffffc0857ffd48: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 160.334446] Object ffffffc0857ffd58: 80 c0 28 47 c1 ff ff ff 00 00 00 00 00 00 00 00 ..(G............
[ 160.344000] Object ffffffc0857ffd68: 80 4a ce d1 c0 ff ff ff dc 32 01 00 01 00 00 00 .J.......2......
[ 160.353554] Object ffffffc0857ffd78: 11 00 ed 41 00 00 00 00 00 00 00 00 00 00 00 00 ...A............
[ 160.363099] Redzone ffffffc0857ffd88: bb bb bb bb bb bb bb bb ........
[ 160.372032] Padding ffffffc0857ffee0: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
[ 160.378299] CPU6: update max cpu_capacity 780
[ 160.380971] CPU: 4 PID: 7098 Comm: syz-executor Tainted: G S B W O 4.14.98+ #1
So, avoid the race by taking a global lock inside uinput_release().
Signed-off-by: Mukesh Ojha <mojha@xxxxxxxxxxxxxx>
Cc: Gaurav Kohli <gkohli@xxxxxxxxxxxxxx>
Cc: Peter Hutterer <peter.hutterer@xxxxxxxxx>
Cc: Martin Kepplinger <martink@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxx>
---
Also, if this looks good we can further use this global lock inside
read/write in separate patches and release can happen at any time.
Changes from v1->v2:
- Mistakenly added udev lock replaced by global lock.
drivers/input/misc/uinput.c | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)
diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 26ec603f..2e7e096 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -81,6 +81,8 @@ struct uinput_device {
spinlock_t requests_lock;
};
+static DEFINE_MUTEX(uinput_glb_mutex);
+
static int uinput_dev_event(struct input_dev *dev,
unsigned int type, unsigned int code, int value)
{
@@ -714,10 +716,18 @@ static __poll_t uinput_poll(struct file *file, poll_table *wait)
static int uinput_release(struct inode *inode, struct file *file)
{
struct uinput_device *udev = file->private_data;
+ ssize_t retval;
+
+ retval = mutex_lock_interruptible(&uinput_glb_mutex);
+ if (retval)
+ return retval;
uinput_destroy_device(udev);
+ file->private_data = NULL;
kfree(udev);
+ mutex_unlock(&uinput_glb_mutex);
+
return 0;
}
@@ -848,7 +858,7 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
unsigned long arg, void __user *p)
{
int retval;
- struct uinput_device *udev = file->private_data;
+ struct uinput_device *udev;
struct uinput_ff_upload ff_up;
struct uinput_ff_erase ff_erase;
struct uinput_request *req;
@@ -856,10 +866,20 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
const char *name;
unsigned int size;
- retval = mutex_lock_interruptible(&udev->mutex);
+ retval = mutex_lock_interruptible(&uinput_glb_mutex);
if (retval)
return retval;
+ udev = file->private_data;
+ if (!udev) {
+ retval = -EINVAL;
+ goto unlock_glb_mutex;
+ }
+
+ retval = mutex_lock_interruptible(&udev->mutex);
+ if (retval)
+ goto unlock_glb_mutex;
+
if (!udev->dev) {
udev->dev = input_allocate_device();
if (!udev->dev) {
@@ -1039,8 +1059,12 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
}
retval = -EINVAL;
+
out:
mutex_unlock(&udev->mutex);
+
+ unlock_glb_mutex:
+ mutex_unlock(&uinput_glb_mutex);
return retval;
}
--
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