CVE-2025-40070

In the Linux kernel, the following vulnerability has been resolved:

pps: fix warning in pps_register_cdev when register device fail

Similar to previous commit 2a934fdb01db ("media: v4l2-dev: fix error handling in __video_register_device()"), the release hook should be set before device_register(). Otherwise, when device_register() return error and put_device() try to callback the release function, the below warning may happen.

------------[ cut here ]------------ WARNING: CPU: 1 PID: 4760 at drivers/base/core.c:2567 device_release+0x1bd/0x240 drivers/base/core.c:2567 Modules linked in: CPU: 1 UID: 0 PID: 4760 Comm: syz.4.914 Not tainted 6.17.0-rc3+ #1 NONE RIP: 0010:device_release+0x1bd/0x240 drivers/base/core.c:2567 Call Trace: <TASK> kobject_cleanup+0x136/0x410 lib/kobject.c:689 kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0xe9/0x130 lib/kobject.c:737 put_device+0x24/0x30 drivers/base/core.c:3797 pps_register_cdev+0x2da/0x370 drivers/pps/pps.c:402 pps_register_source+0x2f6/0x480 drivers/pps/kapi.c:108 pps_tty_open+0x190/0x310 drivers/pps/clients/pps-ldisc.c:57 tty_ldisc_open+0xa7/0x120 drivers/tty/tty_ldisc.c:432 tty_set_ldisc+0x333/0x780 drivers/tty/tty_ldisc.c:563 tiocsetd drivers/tty/tty_io.c:2429 [inline] tty_ioctl+0x5d1/0x1700 drivers/tty/tty_io.c:2728 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl fs/ioctl.c:584 [inline] __x64_sys_ioctl+0x194/0x210 fs/ioctl.c:584 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x5f/0x2a0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK>

Before commit c79a39dc8d06 ("pps: Fix a use-after-free"), pps_register_cdev() call device_create() to create pps->dev, which will init dev->release to device_create_release(). Now the comment is outdated, just remove it.

Thanks for the reminder from Calvin Owens, 'kfree_pps' should be removed in pps_register_source() to avoid a double free in the failure case.

The patch fixes lifetime handling in PPS cdev registration: it sets dev.release before device_register() so that put_device() on failure calls the correct destructor, and it removes a manual kfree(pps) to avoid a potential double free on the error path. Triggering requires PPS/TTY access and forcing device_register() to fail, which is uncommon and typically gated by privileges and system setup. Realistic impact is a low-severity local DoS in rare error paths.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.