CVE-2019-9213

In the Linux kernel before 4.20.14, expand_downwards in mm/mmap.c lacks a check for the mmap minimum address, which makes it easier for attackers to exploit kernel NULL pointer dereferences on non-SMAP platforms. This is related to a capability check for the wrong task.

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0a1d52994d440e21def1c2174932410b4f2a98a1
• http://lists.opensuse.org/opensuse-security-announce/2019-03/msg00045.html
• http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00052.html
• http://packetstormsecurity.com/files/156053/Reliable-Datagram-Sockets-RDS-rds_atomic_free_op-Privilege-Escalation.html
• http://www.securityfocus.com/bid/107296
• https://access.redhat.com/errata/RHSA-2019:0831
• https://access.redhat.com/errata/RHSA-2019:1479
• https://access.redhat.com/errata/RHSA-2019:1480
• https://bugs.chromium.org/p/project-zero/issues/detail?id=1792
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.105
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.27
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20.14
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.162
• https://github.com/torvalds/linux/commit/0a1d52994d440e21def1c2174932410b4f2a98a1
• https://lists.debian.org/debian-lts-announce/2019/03/msg00034.html
• https://lists.debian.org/debian-lts-announce/2019/04/msg00004.html
• https://lists.debian.org/debian-lts-announce/2019/05/msg00002.html
• https://usn.ubuntu.com/3930-1/
• https://usn.ubuntu.com/3930-2/
• https://usn.ubuntu.com/3931-1/
• https://usn.ubuntu.com/3931-2/
• https://usn.ubuntu.com/3932-1/
• https://usn.ubuntu.com/3932-2/
• https://usn.ubuntu.com/3933-1/
• https://usn.ubuntu.com/3933-2/
• https://www.exploit-db.com/exploits/46502/