Description

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

acct: perform last write from workqueue

In [1] it was reported that the acct(2) system call can be used to
trigger NULL deref in cases where it is set to write to a file that
triggers an internal lookup. This can e.g., happen when pointing acc(2)
to /sys/power/resume. At the point the where the write to this file
happens the calling task has already exited and called exit_fs(). A
lookup will thus trigger a NULL-deref when accessing current->fs.

Reorganize the code so that the the final write happens from the
workqueue but with the caller's credentials. This preserves the
(strange) permission model and has almost no regression risk.

This api should stop to exist though.

Classification

CVE ID: CVE-2025-21846

Affected Products

Vendor: Linux, Linux

Product: Linux, Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.02% (probability of being exploited)

EPSS Percentile: 1.78% (scored less or equal to compared to others)

EPSS Date: 2025-04-10 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-21846
https://git.kernel.org/stable/c/5ee8da9bea70dda492d61f075658939af33d8410
https://git.kernel.org/stable/c/5c928e14a2ccd99462f2351ead627b58075bb736
https://git.kernel.org/stable/c/5a59ced8ffc71973d42c82484a719c8f6ac8f7f7
https://git.kernel.org/stable/c/a8136afca090412a36429cb6c2543c714d9c0f84
https://git.kernel.org/stable/c/56d5f3eba3f5de0efdd556de4ef381e109b973a9

Timeline