Description

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

igc: fix PTM cycle trigger logic

Writing to clear the PTM status 'valid' bit while the PTM cycle is
triggered results in unreliable PTM operation. To fix this, clear the
PTM 'trigger' and status after each PTM transaction.

The issue can be reproduced with the following:

$ sudo phc2sys -R 1000 -O 0 -i tsn0 -m

Note: 1000 Hz (-R 1000) is unrealistically large, but provides a way to
quickly reproduce the issue.

PHC2SYS exits with:

"ioctl PTP_OFFSET_PRECISE: Connection timed out" when the PTM transaction
fails

This patch also fixes a hang in igc_probe() when loading the igc
driver in the kdump kernel on systems supporting PTM.

The igc driver running in the base kernel enables PTM trigger in
igc_probe(). Therefore the driver is always in PTM trigger mode,
except in brief periods when manually triggering a PTM cycle.

When a crash occurs, the NIC is reset while PTM trigger is enabled.
Due to a hardware problem, the NIC is subsequently in a bad busmaster
state and doesn't handle register reads/writes. When running
igc_probe() in the kdump kernel, the first register access to a NIC
register hangs driver probing and ultimately breaks kdump.

With this patch, igc has PTM trigger disabled most of the time,
and the trigger is only enabled for very brief (10 - 100 us) periods
when manually triggering a PTM cycle. Chances that a crash occurs
during a PTM trigger are not 0, but extremely reduced.

Classification

CVE ID: CVE-2025-37875

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.03% (probability of being exploited)

EPSS Percentile: 7.64% (scored less or equal to compared to others)

EPSS Date: 2025-06-07 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-37875
https://git.kernel.org/stable/c/c1f174edaccc5a00f8e218c42a0aa9156efd5f76
https://git.kernel.org/stable/c/0c03e4fbe1321697d9d04587e21e416705e1b19f
https://git.kernel.org/stable/c/16194ca3f3b4448a062650c869a7b3b206c6f5d3
https://git.kernel.org/stable/c/f3516229cd12dcd45f23ed01adab17e8772b1bd5
https://git.kernel.org/stable/c/31959e06143692f7e02b8eef7d7d6ac645637906
https://git.kernel.org/stable/c/8e404ad95d2c10c261e2ef6992c7c12dde03df0e

Timeline