CVE-2021-3444

The bpf verifier in the Linux kernel did not properly handle mod32 destination register truncation when the source register was known to be 0. A local attacker with the ability to load bpf programs could use this gain out-of-bounds reads in kernel memory leading to information disclosure (kernel memory), and possibly out-of-bounds writes that could potentially lead to code execution. This issue was addressed in the upstream kernel in commit 9b00f1b78809 (bpf: Fix truncation handling for mod32 dst reg wrt zero) and in Linux stable kernels 5.11.2, 5.10.19, and 5.4.101.

Weakness

When converting from one data type to another, such as long to integer, data can be omitted or translated in a way that produces unexpected values. If the resulting values are used in a sensitive context, then dangerous behaviors may occur.

Affected Software

Potential Mitigations

References

• http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
• http://packetstormsecurity.com/files/164950/Kernel-Live-Patch-Security-Notice-LSN-0082-1.html
• http://www.openwall.com/lists/oss-security/2021/03/23/2
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9b00f1b78809
• https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html
• https://security.netapp.com/advisory/ntap-20210416-0006/
• https://www.openwall.com/lists/oss-security/2021/03/23/2
• http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
• http://packetstormsecurity.com/files/164950/Kernel-Live-Patch-Security-Notice-LSN-0082-1.html
• http://www.openwall.com/lists/oss-security/2021/03/23/2
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9b00f1b78809
• https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html
• https://security.netapp.com/advisory/ntap-20210416-0006/
• https://www.openwall.com/lists/oss-security/2021/03/23/2