Bug 2541182 (CVE-2026-98014)

Summary:	CVE-2026-98014 kernel: net/mlx5: E-Switch, prevent mc_list repopulation during vport disable
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:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Mellanox network driver (mlx5). This vulnerability allows a local privileged user to cause a Denial of Service (DoS) through a system crash. During hardware reset or error recovery procedures, improper cleanup when disabling a virtual network port leaves stale memory references, triggering memory corruption through a use-after-free flaw.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-25 10:55:34 UTC

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

net/mlx5: E-Switch, prevent mc_list repopulation during vport disable

In mlx5_esw_vport_disable(), move esw_apply_vport_rx_mode() ahead
of esw_vport_change_handle_locked() so vport->allmulti_rule is
NULL before the change handler observes it.

During FW-fatal recovery the disable runs while dev->state ==
INTERNAL_ERROR. The promisc query inside esw_update_vport_rx_mode()
fails and returns early, leaving vport->allmulti_rule intact, so
esw_update_vport_mc_promisc() runs and adds MLX5_ACTION_ADD entries
to vport->mc_list whose flow rules are then installed in the FDB
by esw_add_mc_addr(). esw_destroy_legacy_table() tears down the
FDB with those refs still held, corrupting the sub-tree and
leaving dangling flow_rule pointers in vport->mc_list.

Two-stage failure on `echo 1 > /sys/bus/pci/devices/<bdf>/reset`:

  refcount_t: underflow; use-after-free.
   tree_put_node+0xef/0x110 [mlx5_core]
   clean_tree+0x44/0xd0 [mlx5_core] (x5)
   mlx5_fs_core_cleanup+0x57/0x1c0 [mlx5_core]
   mlx5_unload+0x65/0xd0 [mlx5_core]
   ... mlx5_health_try_recover

  BUG: unable to handle page fault for address: 0000000003000055
   down_write+0x1c/0x60
   mlx5_del_flow_rules+0x33/0x1f0 [mlx5_core]
   esw_del_mc_addr+0x7b/0x170 [mlx5_core]
   esw_apply_vport_addr_list+0x56/0xf0 [mlx5_core]
   esw_vport_change_handle_locked+0x28b/0x310 [mlx5_core]
   mlx5_esw_vport_enable+0x270/0x4a0 [mlx5_core]
   ... mlx5_load ... mlx5_health_try_recover

esw_apply_vport_rx_mode(false, false) clears vport->allmulti_rule
via its local state machine even when the FW del fails. With the
rule NULL the !IS_ERR_OR_NULL(allmulti_rule) gate in the change
handler closes, no rules are installed during disable, and the
reload starts with a clean mc_list.

Comment 1 Keith Grant 2026-09-28 19:55:11 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98014.mbox