CVE-2021-47461

Description

In the Linux kernel, the following vulnerability has been resolved: userfaultfd: fix a race between writeprotect and exit_mmap() A race is possible when a process exits, its VMAs are removed by exit_mmap() and at the same time userfaultfd_writeprotect() is called. The race was detected by KASAN on a development kernel, but it appears to be possible on vanilla kernels as well. Use mmget_not_zero() to prevent the race as done in other userfaultfd operations.

CVSS Metrics

• v3.1•MEDIUM•Score: 4.7CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 0.02%• Percentile: 6%

Techniques & Countermeasures

• CWE-362•Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

  The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Systems

• linux•linux

  ≥ 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03, < 3cda4bfffd4f755645577aaa9e96a606657b4525 | ≥ 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03, < 149958ecd0627a9f1e9c678c25c665400054cd6a | ≥ 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03, < cb185d5f1ebf900f4ae3bf84cee212e6dd035aca | 5.7

• linux•linux_kernel

  ≥ 5.7, < 5.10.76 | ≥ 5.11, < 5.14.15 | 5.15:rc1 | 5.15:rc2 | 5.15:rc3 | 5.15:rc4 | 5.15:rc5 | 5.15:rc6

References (3)

• https://git.kernel.org/stable/c/3cda4bfffd4f755645577aaa9e96a606657b4525
• https://git.kernel.org/stable/c/149958ecd0627a9f1e9c678c25c665400054cd6a
• https://git.kernel.org/stable/c/cb185d5f1ebf900f4ae3bf84cee212e6dd035aca