CVE-2021-47506: nfsd: fix use-after-free due to delegation race

Published May 24, 2024
·
Updated

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

nfsd: fix use-after-free due to delegation race

A delegation break could arrive as soon as we've called vfssetlease. A delegation break runs a callback which immediately (in nfsd4cbrecallprepare) adds the delegation to delrecalllru. If we then exit nfs4setdelegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from delrecalllru.

Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread.

I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem. So I'm not sure where the bug was introduced; it may have been there from the beginning.

Affected Software

131 affected componentsFixes available
Linux Linux kernel<4.4.296
Linux Linux kernel>=4.5<4.9.294
Linux Linux kernel>=4.10<4.14.259
Linux Linux kernel>=4.15<4.19.222
Linux Linux kernel>=4.20<5.4.168
Linux Linux kernel>=5.5<5.10.85
Linux Linux kernel>=5.11<5.15.8
Linux Linux kernel=5.15-rc1
Linux Linux kernel=5.15-rc2
Linux Linux kernel=5.15-rc3
Linux Linux kernel=5.15-rc4
ubuntu/linux-azure<4.15.0-1131.144~14.04.1
4.15.0-1131.144~14.04.1
ubuntu/linux*
ubuntu/linux-aws<4.4.0-1143.149
4.4.0-1143.149
ubuntu/linux-lts-xenial<4.4.0-268.302~14.04.1
4.4.0-268.302~14.04.1
ubuntu/linux<4.4.0-268.302
4.4.0-268.302
ubuntu/linux-aws<4.4.0-1181.196
4.4.0-1181.196
ubuntu/linux-aws-hwe<4.15.0-1120.128~16.04.1
4.15.0-1120.128~16.04.1
ubuntu/linux-azure<4.15.0-1131.144~16.04.1
4.15.0-1131.144~16.04.1
ubuntu/linux-gcp<4.15.0-1116.130~16.04.1
4.15.0-1116.130~16.04.1
ubuntu/linux-hwe<4.15.0-169.177~16.04.1
4.15.0-169.177~16.04.1
ubuntu/linux-kvm<4.4.0-1144.155
4.4.0-1144.155
ubuntu/linux-oracle<4.15.0-1087.95~16.04.1
4.15.0-1087.95~16.04.1
ubuntu/linux-hwe-edge*
ubuntu/linux-fips<4.4.0-1113.120
4.4.0-1113.120
ubuntu/linux-fips*
ubuntu/linux<4.15.0-169.177
4.15.0-169.177
ubuntu/linux-aws<4.15.0-1121.129
4.15.0-1121.129
ubuntu/linux-aws-5.4<5.4.0-1069.73~18.04.1
5.4.0-1069.73~18.04.1
ubuntu/linux-azure-4.15<4.15.0-1131.144
4.15.0-1131.144
ubuntu/linux-azure-5.4<5.4.0-1073.76~18.04.1
5.4.0-1073.76~18.04.1
ubuntu/linux-gcp-4.15<4.15.0-1116.130
4.15.0-1116.130
ubuntu/linux-gcp-5.4<5.4.0-1068.72~18.04.1
5.4.0-1068.72~18.04.1
ubuntu/linux-hwe-5.4<5.4.0-105.119~18.04.1
5.4.0-105.119~18.04.1
ubuntu/linux-ibm-5.4<5.4.0-1018.20~18.04.1
5.4.0-1018.20~18.04.1
ubuntu/linux-kvm<4.15.0-1107.109
4.15.0-1107.109
ubuntu/linux-oracle<4.15.0-1087.95
4.15.0-1087.95
ubuntu/linux-oracle-5.4<5.4.0-1067.72~18.04.1
5.4.0-1067.72~18.04.1
ubuntu/linux-raspi-5.4<5.4.0-1056.63~18.04.1
5.4.0-1056.63~18.04.1
ubuntu/linux-aws-5.0*
ubuntu/linux-aws-5.3*
ubuntu/linux-azure*
ubuntu/linux-azure-5.3*
ubuntu/linux-azure-edge*
ubuntu/linux-gcp*
ubuntu/linux-gcp-5.3*
ubuntu/linux-gke-4.15*
ubuntu/linux-gke-5.4*
ubuntu/linux-gkeop-5.4*
ubuntu/linux-hwe*
ubuntu/linux-hwe-edge*
ubuntu/linux-oem*
ubuntu/linux-oracle-5.0*
ubuntu/linux-oracle-5.3*
ubuntu/linux-aws-fips<4.15.0-2061.63
4.15.0-2061.63
ubuntu/linux-azure-fips<4.15.0-2043.47
4.15.0-2043.47
ubuntu/linux-fips<4.15.0-1078.87
4.15.0-1078.87
ubuntu/linux-gcp-fips<4.15.0-2026.28
4.15.0-2026.28
ubuntu/linux-aws-fips*
ubuntu/linux-azure-fips*
ubuntu/linux-fips*
ubuntu/linux-gcp-fips*
ubuntu/linux<5.4.0-105.119
5.4.0-105.119
ubuntu/linux-aws<5.4.0-1069.73
5.4.0-1069.73
ubuntu/linux-azure<5.4.0-1073.76
5.4.0-1073.76
ubuntu/linux-bluefield<5.4.0-1032.35
5.4.0-1032.35
ubuntu/linux-gcp<5.4.0-1068.72
5.4.0-1068.72
ubuntu/linux-gkeop<5.4.0-1037.38
5.4.0-1037.38
ubuntu/linux-ibm<5.4.0-1018.20
5.4.0-1018.20
ubuntu/linux-kvm<5.4.0-1059.62
5.4.0-1059.62
ubuntu/linux-oracle<5.4.0-1067.72
5.4.0-1067.72
ubuntu/linux-raspi<5.4.0-1056.63
5.4.0-1056.63
ubuntu/linux-aws-5.11*
ubuntu/linux-aws-5.13*
ubuntu/linux-aws-5.8*
ubuntu/linux-azure-5.11*
ubuntu/linux-azure-5.13*
ubuntu/linux-azure-5.8*
ubuntu/linux-azure-fde*
ubuntu/linux-gcp-5.11*
ubuntu/linux-gcp-5.13*
ubuntu/linux-gcp-5.8*
ubuntu/linux-gke*
ubuntu/linux-gke-5.15*
ubuntu/linux-hwe-5.11*
ubuntu/linux-hwe-5.13*
ubuntu/linux-hwe-5.8*
ubuntu/linux-intel-5.13*
ubuntu/linux-oem-5.10*
ubuntu/linux-oem-5.13*
ubuntu/linux-oem-5.6*
ubuntu/linux-oracle-5.11*
ubuntu/linux-oracle-5.13*
ubuntu/linux-oracle-5.8*
ubuntu/linux-raspi2*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.11*
ubuntu/linux-riscv-5.8*
ubuntu/linux-aws-fips<5.4.0-1069.73+fips2
5.4.0-1069.73+fips2
ubuntu/linux-azure-fips<5.4.0-1073.76+fips1
5.4.0-1073.76+fips1
ubuntu/linux-fips<5.4.0-1046.52
5.4.0-1046.52
ubuntu/linux-gcp-fips<5.4.0-1067.71~20.04.1
5.4.0-1067.71~20.04.1
ubuntu/linux-aws-fips*
ubuntu/linux-azure-fips*
ubuntu/linux-fips*
ubuntu/linux-gcp-fips*
ubuntu/linux-allwinner-5.19*
ubuntu/linux-aws-5.19*
ubuntu/linux-aws-6.2*
ubuntu/linux-azure-5.19*
ubuntu/linux-azure-6.2*
ubuntu/linux-azure-fde-5.19*
ubuntu/linux-azure-fde-6.2*
ubuntu/linux-gcp-5.19*
ubuntu/linux-gcp-6.2*
ubuntu/linux-hwe-5.19*
ubuntu/linux-hwe-6.2*
ubuntu/linux-intel-iot-realtime*
ubuntu/linux-lowlatency-hwe-5.19*
ubuntu/linux-lowlatency-hwe-6.2*
ubuntu/linux-nvidia-6.2*
ubuntu/linux-oem-5.17*
ubuntu/linux-oem-6.0*
ubuntu/linux-oem-6.1*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.19*
ubuntu/linux-starfive-5.19*
ubuntu/linux-starfive-6.2*
ubuntu/linux-raspi-realtime*
ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 4.15.0-1131.144~14.04.1
  2. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 4.4.0-1143.149
  3. Upgrade

    Upgrade ubuntu/linux-lts-xenial to a version that resolves this vulnerability.

    Fixed in 4.4.0-268.302~14.04.1
  4. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 4.4.0-268.302
  5. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 4.4.0-1181.196
  6. Upgrade

    Upgrade ubuntu/linux-aws-hwe to a version that resolves this vulnerability.

    Fixed in 4.15.0-1120.128~16.04.1
  7. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 4.15.0-1131.144~16.04.1
  8. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 4.15.0-1116.130~16.04.1
  9. Upgrade

    Upgrade ubuntu/linux-hwe to a version that resolves this vulnerability.

    Fixed in 4.15.0-169.177~16.04.1
  10. Upgrade

    Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.

    Fixed in 4.4.0-1144.155
  11. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 4.15.0-1087.95~16.04.1
  12. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 4.4.0-1113.120
  13. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 4.15.0-169.177
  14. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 4.15.0-1121.129
  15. Upgrade

    Upgrade ubuntu/linux-aws-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1069.73~18.04.1
  16. Upgrade

    Upgrade ubuntu/linux-azure-4.15 to a version that resolves this vulnerability.

    Fixed in 4.15.0-1131.144
  17. Upgrade

    Upgrade ubuntu/linux-azure-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1073.76~18.04.1
  18. Upgrade

    Upgrade ubuntu/linux-gcp-4.15 to a version that resolves this vulnerability.

    Fixed in 4.15.0-1116.130
  19. Upgrade

    Upgrade ubuntu/linux-gcp-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1068.72~18.04.1
  20. Upgrade

    Upgrade ubuntu/linux-hwe-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-105.119~18.04.1
  21. Upgrade

    Upgrade ubuntu/linux-ibm-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1018.20~18.04.1
  22. Upgrade

    Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.

    Fixed in 4.15.0-1107.109
  23. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 4.15.0-1087.95
  24. Upgrade

    Upgrade ubuntu/linux-oracle-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1067.72~18.04.1
  25. Upgrade

    Upgrade ubuntu/linux-raspi-5.4 to a version that resolves this vulnerability.

    Fixed in 5.4.0-1056.63~18.04.1
  26. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 4.15.0-2061.63
  27. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 4.15.0-2043.47
  28. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 4.15.0-1078.87
  29. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 4.15.0-2026.28
  30. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 5.4.0-105.119
  31. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 5.4.0-1069.73
  32. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 5.4.0-1073.76
  33. Upgrade

    Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.

    Fixed in 5.4.0-1032.35
  34. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 5.4.0-1068.72
  35. Upgrade

    Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.

    Fixed in 5.4.0-1037.38
  36. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 5.4.0-1018.20
  37. Upgrade

    Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.

    Fixed in 5.4.0-1059.62
  38. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 5.4.0-1067.72
  39. Upgrade

    Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.

    Fixed in 5.4.0-1056.63
  40. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 5.4.0-1069.73+fips2
  41. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 5.4.0-1073.76+fips1
  42. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 5.4.0-1046.52
  43. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 5.4.0-1067.71~20.04.1

Event History

May 24, 2024
CVE Published
via MITRE·03:01 PM
Data Sourced
via MITRE·03:01 PM
DescriptionSeverity
Data Sourced
via OSV·03:15 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·03:15 PM
RemedyDescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

1

What is the severity of CVE-2021-47506?

CVE-2021-47506 is classified as a medium severity vulnerability in the Linux kernel due to the potential for use-after-free issues.

2

How do I fix CVE-2021-47506?

To fix CVE-2021-47506, update your Linux kernel to a version beyond the affected versions up to 5.15-rc4.

3

What versions of the Linux kernel are affected by CVE-2021-47506?

CVE-2021-47506 affects Linux kernel versions from 4.4.0 to 5.15-rc4.

4

What is the impact of CVE-2021-47506 on system security?

CVE-2021-47506 can lead to a use-after-free condition which may allow an attacker to execute arbitrary code in the kernel.

5

Is CVE-2021-47506 actively exploited in the wild?

As of now, there is no specific evidence indicating that CVE-2021-47506 is actively exploited in the wild.

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