powerpc/64s: Fix crashes when toggling entry flush barrier
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 2 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.
Summary
In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Fix crashes when toggling entry flush barrier The entry flush mitigation can be enabled/disabled at runtime via a debugfs file (entry_flush), which causes the kernel to patch itself to enable/disable the relevant mitigations. However depending on which mitigation we're using, it may not be safe to do that patching while other CPUs are active. For example the following crash: sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20 Shows that we returned to userspace with a corrupted LR that points into the kernel, due to executing the partially patched call to the fallback entry flush (ie. we missed the LR restore). Fix it by doing the patching under stop machine. The CPUs that aren't doing the patching will be spinning in the core of the stop machine logic. That is currently sufficient for our purposes, because none of the patching we do is to that code or anywhere in the vicinity.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 4.4.245 to before 4.4.269; 4.9.245 to before 4.9.269; 4.14.208 to before 4.14.233; 4.19.159 to before 4.19.191; 5.4.79 to before 5.4.120; 5.9.10 to before 5.10 | 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.120, 5.10 | Patch available | CNA |
| Linux | Linux | 5.10 and later | 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.120, 5.10.38, 5.11.22, 5.12.5, 5.13 | Patch available | CNA |
- Linux VendorLinux Affected 4.4.245 to before 4.4.269; 4.9.245 to before 4.9.269; 4.14.208 to before 4.14.233; 4.19.159 to before 4.19.191; 5.4.79 to before 5.4.120; 5.9.10 to before 5.10 Fixed in 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.120, 5.10 Patch available CNA
- Linux VendorLinux Affected 5.10 and later Fixed in 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.120, 5.10.38, 5.11.22, 5.12.5, 5.13 Patch available CNA
CPE configurations NVD · 2
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 4.4.245 to before 4.4.269; 4.9.245 to before 4.9.269; 4.14.208 to before 4.14.233; 4.19.159 to before 4.19.191; 5.4.79 to before 5.4.120; 5.10 to before 5.10.38; 5.11 to before 5.11.22; 5.12 to before 5.12.5 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:* | 5.13 rc1 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 4.4.245 to before 4.4.269; 4.9.245 to before 4.9.269; 4.14.208 to before 4.14.233; 4.19.159 to before 4.19.191; 5.4.79 to before 5.4.120; 5.10 to before 5.10.38; 5.11 to before 5.11.22; 5.12 to before 5.12.5 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:* Versions 5.13 rc1 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.120, 5.10
- Fix · CNA Linux (Linux) Fixed in 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.120, 5.10.38, 5.11.22, 5.12.5, 5.13
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
Not affected: 2 products
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2021-46990
- 2026-10-03 Alias added: GHSA-qg29-4gg5-8r2w
References
Patch 9
- https://git.kernel.org/stable/c/8382b15864e5014261b4f36c2aa89723612ee058
- https://git.kernel.org/stable/c/0c25a7bb697f2e6ee65b6d63782f675bf129511a
- https://git.kernel.org/stable/c/ee4b7aab93c2631c3bb0753023c5dda592bb666b
- https://git.kernel.org/stable/c/2db22ba4e0e103f00e0512e0ecce36ac78c644f8
- https://git.kernel.org/stable/c/0b4eb172cc12dc102cd0ad013e53ee4463db9508
- https://git.kernel.org/stable/c/d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92
- https://git.kernel.org/stable/c/dd0d6117052faace5440db20fc37175efe921c7d
- https://git.kernel.org/stable/c/5bc00fdda1e934c557351a9c751a205293e68cbf
- https://git.kernel.org/stable/c/aec86b052df6541cc97c5fca44e5934cbea4963b
More Linux Kernel vulnerabilities
- TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
- TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
- TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
- TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
- TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
- TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
Sources
- CVE-2021-46990 · CVE Program
- CVE-2021-46990 · NVD
- FIRST EPSS
- GHSA-qg29-4gg5-8r2w · GitHub Advisory Database · CC BY 4.0
- CVE-2021-46990 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences