Bug 2555056 (CVE-2026-98798)

Summary:	CVE-2026-98798 kernel: net: bcmgenet: fix NULL dereference in set_coalesce before first open
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 Broadcom GENET network driver. A privileged local user could trigger a Denial of Service (DoS) by configuring receive coalescing settings on a network interface that has not yet been opened. This flaw leads to a null pointer dereference that can crash the kernel or lock networking operations, requiring a system reboot to restore service.	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 2026-10-18 15:51:57 UTC

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

net: bcmgenet: fix NULL dereference in set_coalesce before first open

The Rx ring priv and index are only set in bcmgenet_init_rx_ring(),
which runs at open. Setting the Rx coalescing parameters on an interface
that was never opened, e.g. "ethtool -C eth0 rx-usecs 50", dereferences
a NULL ring->priv. The oops happens with RTNL held, so networking
stays stuck until a reboot:

  Unable to handle kernel paging request at virtual address 0000000000002788
  pc : bcmgenet_set_rx_coalesce.isra.0+0x10/0x88
  lr : bcmgenet_set_coalesce+0xe8/0x180
  Call trace:
   bcmgenet_set_rx_coalesce.isra.0+0x10/0x88 (P)
   __ethnl_set_coalesce.isra.0+0x490/0x570
   ethnl_set_coalesce+0x48/0xc0
   ethnl_default_set_doit+0xf4/0x230
   genl_family_rcv_msg_doit+0xe8/0x160
   genl_rcv_msg+0x220/0x2a0
   netlink_rcv_skb+0x68/0x140
   genl_rcv+0x40/0x60
   netlink_unicast+0x338/0x3c0
   netlink_sendmsg+0x19c/0x3f8
   __sock_sendmsg+0x64/0xc0
   __sys_sendto+0x124/0x198
   __arm64_sys_sendto+0x30/0x48

Set priv and index at probe. Writing the registers while the interface
is down is harmless because open resets the MAC and
bcmgenet_init_rx_coalesce() reapplies the stored values.

It was observed on a Raspberry Pi CM4, but should apply to all other
genet devices.

Comment 1 Mauro Matteo Cascella 2026-10-23 12:56:45 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98798.mbox