Medium · published September 15, 2025
In the Linux kernel, the following vulnerability has been resolved:
watchdog: Fix kmemleak in watchdog_cdev_register
kmemleak reports memory leaks in watchdog_dev_register, as follows:
unreferenced object 0xffff888116233000 (size 2048):
comm ""modprobe"", pid 28147, jiffies 4353426116 (age 61.741s)
hex dump (first 32 bytes):
80 fa b9 05 81 88 ff ff 08 30 23 16 81 88 ff ff .........0#.....
08 30 23 16 81 88 ff ff 00 00 00 00 00 00 00 00 .0#.............
backtrace:
[<000000007f001ffd>] __kmem_cache_alloc_node+0x157/0x220
[<000000006a389304>] kmalloc_trace+0x21/0x110
[<000000008d640eea>] watchdog_dev_register+0x4e/0x780 [watchdog]
[<0000000053c9f248>] __watchdog_register_device+0x4f0/0x680 [watchdog]
[<00000000b2979824>] watchdog_register_device+0xd2/0x110 [watchdog]
[<000000001f730178>] 0xffffffffc10880ae
[<000000007a1a8bcc>] do_one_initcall+0xcb/0x4d0
[<00000000b98be325>] do_init_module+0x1ca/0x5f0
[<0000000046d08e7c>] load_module+0x6133/0x70f0
...
unreferenced object 0xffff888105b9fa80 (size 16):
comm ""modprobe"", pid 28147, jiffies 4353426116 (age 61.741s)
hex dump (first 16 bytes):
77 61 74 63 68 64 6f 67 31 00 b9 05 81 88 ff ff watchdog1.......
backtrace:
[<000000007f001ffd>] __kmem_cache_alloc_node+0x157/0x220
[<00000000486ab89b>] __kmalloc_node_track_caller+0x44/0x1b0
[<000000005a39aab0>] kvasprintf+0xb5/0x140
[<0000000024806f85>] kvasprintf_const+0x55/0x180
[<000000009276cb7f>] kobject_set_name_vargs+0x56/0x150
[<00000000a92e820b>] dev_set_name+0xab/0xe0
[<00000000cec812c6>] watchdog_dev_register+0x285/0x780 [watchdog]
[<0000000053c9f248>] __watchdog_register_device+0x4f0/0x680 [watchdog]
[<00000000b2979824>] watchdog_register_device+0xd2/0x110 [watchdog]
[<000000001f730178>] 0xffffffffc10880ae
[<000000007a1a8bcc>] do_one_initcall+0xcb/0x4d0
[<00000000b98be325>] do_init_module+0x1ca/0x5f0
[<0000000046d08e7c>] load_module+0x6133/0x70f0
...
The reason is that put_device is not be called if cdev_device_add fails
and wdd->id != 0.
watchdog_cdev_register
wd_data = kzalloc [1]
err = dev_set_name [2]
..
err = cdev_device_add
if (err) {
if (wdd->id == 0) { // wdd->id != 0
..
}
return err; // [1],[2] would be leaked
To fix it, call put_device in all wdd->id cases.