Bug 2315209 (CVE-2024-46857)

Summary:	CVE-2024-46857 kernel: net/mlx5: Fix bridge mode operations when there are no VFs
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dfreiber, drow, jburrell, rhel-process-autobot, vkumar, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	A flaw was found in the Linux kernel's `net/mlx5` driver. A local attacker can trigger a null pointer dereference by attempting to configure bridge mode operations when no Virtual Functions (VFs) are present. This vulnerability can lead to a kernel crash, resulting in a denial of service (DoS) for the affected system.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
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Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2315247
Bug Blocks:

Description OSIDB Bzimport 2024-09-27 13:23:08 UTC

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5: Fix bridge mode operations when there are no VFs

Currently, trying to set the bridge mode attribute when numvfs=0 leads to a
crash:

bridge link set dev eth2 hwmode vepa

[  168.967392] BUG: kernel NULL pointer dereference, address: 0000000000000030
[...]
[  168.969989] RIP: 0010:mlx5_add_flow_rules+0x1f/0x300 [mlx5_core]
[...]
[  168.976037] Call Trace:
[  168.976188]  <TASK>
[  168.978620]  _mlx5_eswitch_set_vepa_locked+0x113/0x230 [mlx5_core]
[  168.979074]  mlx5_eswitch_set_vepa+0x7f/0xa0 [mlx5_core]
[  168.979471]  rtnl_bridge_setlink+0xe9/0x1f0
[  168.979714]  rtnetlink_rcv_msg+0x159/0x400
[  168.980451]  netlink_rcv_skb+0x54/0x100
[  168.980675]  netlink_unicast+0x241/0x360
[  168.980918]  netlink_sendmsg+0x1f6/0x430
[  168.981162]  ____sys_sendmsg+0x3bb/0x3f0
[  168.982155]  ___sys_sendmsg+0x88/0xd0
[  168.985036]  __sys_sendmsg+0x59/0xa0
[  168.985477]  do_syscall_64+0x79/0x150
[  168.987273]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  168.987773] RIP: 0033:0x7f8f7950f917

(esw->fdb_table.legacy.vepa_fdb is null)

The bridge mode is only relevant when there are multiple functions per
port. Therefore, prevent setting and getting this setting when there are no
VFs.

Note that after this change, there are no settings to change on the PF
interface using `bridge link` when there are no VFs, so the interface no
longer appears in the `bridge link` output.

Comment 1 Robb Gatica 2024-09-27 14:38:10 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2024092743-CVE-2024-46857-3bc3@gregkh/T