CVE-2020-25220

The Linux kernel 4.9.x before 4.9.233, 4.14.x before 4.14.194, and 4.19.x before 4.19.140 has a use-after-free because skcd->no_refcnt was not considered during a backport of a CVE-2020-14356 patch. This is related to the cgroups feature.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1868453
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.194
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.140
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.233
• https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y\u0026id=82fd2138a5ffd7e0d4320cdb669e115ee976a26e
• https://lists.debian.org/debian-lts-announce/2020/10/msg00032.html
• https://lists.debian.org/debian-lts-announce/2020/10/msg00034.html
• https://security.netapp.com/advisory/ntap-20201001-0004/
• https://www.spinics.net/lists/stable/msg405099.html
• https://bugzilla.redhat.com/show_bug.cgi?id=1868453
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.194
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.140
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.233
• https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y\u0026id=82fd2138a5ffd7e0d4320cdb669e115ee976a26e
• https://lists.debian.org/debian-lts-announce/2020/10/msg00032.html
• https://lists.debian.org/debian-lts-announce/2020/10/msg00034.html
• https://security.netapp.com/advisory/ntap-20201001-0004/
• https://www.spinics.net/lists/stable/msg405099.html