CVE-2026-45940: net: stmmac: fix oops when split header is enabled
In the Linux kernel, the following vulnerability has been resolved:
net: stmmac: fix oops when split header is enabled
For GMAC4, when split header is enabled, in some rare cases, the hardware does not fill buf2 of the first descriptor with payload. Thus we cannot assume buf2 is always fully filled if it is not the last descriptor. Otherwise, the length of buf2 of the second descriptor will be calculated wrong and cause an oops:
Unable to handle kernel paging request at virtual address ffff00019246bfc0 ... x2 : 0000000000000040 x1 : ffff00019246bfc0 x0 : ffff00009246c000 Call trace: dcacheinvalpoc+0x28/0x58 (P) dmadirectsyncsingleforcpu+0x38/0x6c dmasyncsingleforcpu+0x34/0x6c stmmacnapipollrx+0x8f0/0xb60 napipoll.constprop.0+0x30/0x144 netrxaction+0x160/0x274 handlesoftirqs+0x1b8/0x1fc ...
To fix this, the PL bit-field in RDES3 register is used for all descriptors, whether it is the last descriptor or not.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
linux/Kernelto a version that resolves this vulnerability.Fixed in 6.1.191 - Upgrade
Upgrade
linux/Kernelto a version that resolves this vulnerability.Fixed in 6.6.160 - Upgrade
Upgrade
linux/Kernelto a version that resolves this vulnerability.Fixed in 6.12.114 - Upgrade
Upgrade
linux/Kernelto a version that resolves this vulnerability.Fixed in 6.18.14 - Upgrade
Upgrade
linux/Kernelto a version that resolves this vulnerability.Fixed in 6.19.4 - Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 6.18.14-1 - Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 7.2.12-1Fixed in 7.2.14-1
Event History
Frequently Asked Questions
Which systems are affected in practice?
The issue applies to Linux systems using the stmmac driver with GMAC4 hardware when split-header mode is enabled. The listed affected software includes the Linux kernel and Ubuntu kernel variants for Azure, GCP, AWS FIPS, FIPS, and realtime deployments.
What conditions are needed to trigger the failure?
Split-header mode must be enabled on GMAC4 hardware. In rare receive-path cases where hardware does not place payload data in buf2 of the first descriptor, the driver can calculate the next descriptor's buf2 length incorrectly and trigger a kernel paging-request oops.
What is the operational impact?
The failure occurs in the stmmac NAPI receive polling path and can cause a kernel oops due to an invalid memory access. The provided vector indicates local access, low attack complexity, low privileges, no user interaction, and an availability impact.
How does the fix prevent the crash?
The fix uses the PL bit field in the RDES3 register to determine payload length for every descriptor, not only the final descriptor. This avoids assuming that buf2 is fully populated on non-final descriptors.