CVE-2025-38621

md: make rdev_addable usable for rcu mode

Description

In the Linux kernel, the following vulnerability has been resolved: md: make rdev_addable usable for rcu mode Our testcase trigger panic: BUG: kernel NULL pointer dereference, address: 00000000000000e0 ... Oops: Oops: 0000 [#1] SMP NOPTI CPU: 2 UID: 0 PID: 85 Comm: kworker/2:1 Not tainted 6.16.0+ #94 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Workqueue: md_misc md_start_sync RIP: 0010:rdev_addable+0x4d/0xf0 ... Call Trace: <TASK> md_start_sync+0x329/0x480 process_one_work+0x226/0x6d0 worker_thread+0x19e/0x340 kthread+0x10f/0x250 ret_from_fork+0x14d/0x180 ret_from_fork_asm+0x1a/0x30 </TASK> Modules linked in: raid10 CR2: 00000000000000e0 ---[ end trace 0000000000000000 ]--- RIP: 0010:rdev_addable+0x4d/0xf0 md_spares_need_change in md_start_sync will call rdev_addable which protected by rcu_read_lock/rcu_read_unlock. This rcu context will help protect rdev won't be released, but rdev->mddev will be set to NULL before we call synchronize_rcu in md_kick_rdev_from_array. Fix this by using READ_ONCE and check does rdev->mddev still alive.

N/A

CVSS

Severity:

EPSS 0.02%

Affected: Linux Linux

References

Link	Tags
https://git.kernel.org/stable/c/b5fbe940862339cdcc34dea7a057ad18d18fa137
https://git.kernel.org/stable/c/13017b427118f4311471ee47df74872372ca8482

Frequently Asked Questions

What is the severity of CVE-2025-38621?: CVE-2025-38621 has not yet been assigned a CVSS score.
How to fix CVE-2025-38621?: To fix CVE-2025-38621, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2025-38621 being actively exploited in the wild?: As for now, there are no information to confirm that CVE-2025-38621 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-38621?: CVE-2025-38621 affects Linux Linux, Linux Linux.

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