Bug 1663729 (CVE-2019-3701)

Summary:	CVE-2019-3701 kernel: Missing check in net/can/gw.c:can_can_gw_rcv() allows for crash by users with CAP_NET_ADMIN
Product:	[Other] Security Response	Reporter:	Sam Fowler <sfowler>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	vdronov
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	An issue was discovered in can_can_gw_rcv() in the net/can/gw.c in the Linux kernel. The CAN driver may write arbitrary content beyond the data registers in the CAN controller's I/O memory when processing can-gw manipulated outgoing frames because of a missing check. A local user with CAP_NET_ADMIN capability granted in the initial namespace can exploit this vulnerability to cause a system crash and thus a denial of service (DoS).	Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-03-14 17:06:04 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1663730
Bug Blocks:	1663768

Description Sam Fowler 2019-01-07 03:02:30 UTC

An issue was discovered in can_can_gw_rcv() in the net/can/gw.c in the Linux kernel. The CAN driver may write an arbitrary content beyond the data registers in the CAN controller's I/O memory when processing can-gw manipulated outgoing frames because of a missing check. A local user with CAP_NET_ADMIN capability granted in the initial namespace can exploit this vulnerability to cause a system crash and thus a denial of service (DoS).

References:

https://marc.info/?t=154651855000001&r=1&w=2

A suggested patch:

https://marc.info/?l=linux-can&m=154659326224990&w=2

An upstream patch:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0aaa81377c5a01f686bcdb8c7a6929a7bf330c68

Comment 1 Sam Fowler 2019-01-07 03:02:45 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1663730]

Comment 2 Vladis Dronov 2019-03-14 16:45:11 UTC

Exploitability and Impact Note:

https://marc.info/?l=linux-can&m=154654764312859&w=2

From:       Michal Kubecek <mkubecek () suse ! cz>

> > Second can-gw rules can only be configured by *root* and not by any regular
> > user - and finally it is definitely not namespace related.
> 
> Sorry for the noise, I misread the code (and commit 90f62cf30a78) so
> that I thought netlink_ns_capable() is used in net/can/gw.c; now I see
> that it's netlink_capable() so that global CAP_NET_ADMIN is required
> rather than namespace one and the bug cannot be exploited by a regular
> user.

With this noted we consider this issue to be a bug and not a security flaw.