Bug 2555207 (CVE-2026-98807)

Summary: CVE-2026-98807 kernel: net/mlx5: Fix slab-out-of-bounds when handling team device events
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: 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   
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A flaw was found in the Linux kernel's Mellanox ConnectX (mlx5) network driver. It allows a privileged local user to cause a Denial of Service (DoS) via an out-of-bounds memory read. When processing Link Aggregation (LAG) events, the driver incorrectly applies bonding-specific operations to smaller network team data structures. Triggering these configuration events causes the driver to access memory outside allocated bounds, resulting in a kernel panic and system crash.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-10-18 16:01:55 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net/mlx5: Fix slab-out-of-bounds when handling team device events

The mlx5_handle_changeupper_event() and mlx5_handle_changeinfodata_event()
functions check for LAG masters (which includes both bonding and team
devices) but only call bonding-specific APIs. When processing team device
events, calling bond_slave_get_rcu() and bond_is_slave_inactive() on
team_port structures causes KASAN to detect an out-of-bounds memory access
since team_port is smaller than bond slave.

Fix this by wrapping the bond-specific API calls with a check for bonding
devices. This allows the function to still process LAG events for both
bonding and teams but only calls bond-specific functions when dealing with
actual bonding devices.

For mlx5_handle_changeinfodata_event(), keep the explicit bond check as
mlx5 doesn't handle state information for team ports anyway.

Tested with Mellanox ConnectX-5 on Linux 7.2.0-rc6:
- Bonding: PASS (no regressions)
- Team device: PASS (no KASAN errors)
Comment 1 Mauro Matteo Cascella 2026-10-23 16:36:56 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98807.mbox