A local user can trigger a flaw in the Linux kernel's handling of key lookups in the keychain subsystem.

The keyrejectandlink() function contains an error in which a key-lookup can fail and in an attempt to cache the failed lookup may attempt to free memory which can still be in use.

This could crash the system or at worse free a memory block which would then be re-used by another kernel mechanism causing a user after free.

Product bug:

https://bugzilla.redhat.com/showbug.cgi?id=1341352

Upstream patch:

https://www.spinics.net/lists/linux-kernel-janitors/msg26069.html

A use-after-free vulnerability was found in a network namespaces code affecting the Linux kernel since v4.0-rc1 through v4.15-rc5. The function getnetnsbyid() does not check for the net::count value after it has found a peer network in netnsids idr which could lead to double free and memory corruption. This vulnerability could allow an unprivileged local user to induce kernel memory corruption on the system, leading to a crash. Due to the nature of the flaw, privilege escalation cannot be fully ruled out, although we believe it is unlikely.

References:

https://marc.info/?l=linux-netdev&m=151370451121029&w=2

https://marc.info/?t=151370468900001&r=1&w=2 (a whole thread)

http://seclists.org/oss-sec/2018/q1/7

An upstream patch:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=21b5944350052d2583e82dd59b19a9ba94a007f0