CVE request -- linux kernel: crash by spawning mcrypt(alg) with incompatible algorithm

[Vladis Dronov <vdronov () redhat com>]

Hello,

Algorithms not compatible with mcryptd could be spawned by mcryptd with a direct
crypto_alloc_tfm invocation using a "mcryptd(alg)" name construct. This causes
mcryptd to crash the kernel if an arbitrary "alg" is incompatible and not intended
to be used with mcryptd.

This could be a potential attack to crash the kernel by user program using AF_ALG
to request an invalid algorithm such as mcryptd(md5).

Initial discussion:

https://marc.info/?l=dm-devel&m=148063708010538&w=2

Suggested Patch:

http://marc.info/?l=linux-crypto-vger&m=148096718218312&w=2

Upstream patch:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=48a992727d82cb7db076fa15d372178743b1f4cd

Red Hat Product Security Bugzilla:

https://bugzilla.redhat.com/show_bug.cgi?id=1404200

Best regards,
Vladis Dronov | Red Hat, Inc. | Product Security Engineer