Linux kernel bonding driver null-deref in bond_alb_monitor (CVE-2026-74726)
CVE-2026-74726 Published on August 22, 2026
bonding: alb: re-check primary_is_promisc under RTNL in bond_alb_monitor
In the Linux kernel, the following vulnerability has been resolved:
bonding: alb: re-check primary_is_promisc under RTNL in bond_alb_monitor
bond_alb_monitor() reads primary_is_promisc under RCU, then drops RCU and
takes RTNL via rtnl_trylock() before undoing the promiscuity it set on the
active slave. In that window the active slave can change under RTNL
(RTM_DELLINK -> __bond_release_one() -> bond_alb_handle_active_change()),
which already drops the promiscuity and clears primary_is_promisc. The
monitor still acts on the stale decision: if the slave was removed with no
failover, curr_active_slave is now NULL and the deref faults; if it failed
over, the stale dev_set_promiscuity(-1) underflows the new slave's
promiscuity counter and pins it in IFF_PROMISC.
Oops: general protection fault, probably for non-canonical address ...
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
Workqueue: b42 bond_alb_monitor
RIP: 0010:bond_alb_monitor (drivers/net/bonding/bond_alb.c:1600)
process_one_work (kernel/workqueue.c:3322)
worker_thread (kernel/workqueue.c:3486)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
Kernel panic - not syncing: Fatal exception
Re-check primary_is_promisc (and curr_active_slave) after taking RTNL so
the monitor only undoes an increment it still owns. The other bonding
monitors already re-read state under RTNL in their commit phase
(bond_miimon_commit/bond_ab_arp_commit); bond_alb_monitor() was the only
one acting on the pre-trylock decision.
Products Associated with CVE-2026-74726
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Affected Versions
Linux:- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below f7668762bf5fd6db9397de5c0514407489d9d815 is affected.
- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below 09add8d5cfa9c46828f51eaad162c36e86366b71 is affected.
- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below b82f51681a7a88c7d3c865e817a3340d42b5fa2a is affected.
- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below dd148539fb4741d01c06b7d2c8bd84b01920756c is affected.
- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below dccec0227ed8d9e36936d66e256b957dc2858468 is affected.
- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below 2faf75a8a06504071b4c0aea7e45a9cc49a4e187 is affected.
- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below 257c4a3a34d8f51efb00f35375a0c6ce3c8f6ce2 is affected.
- Version d0e81b7e2246a41d068ecaf15aac9de570816d63 and below 683c6ba6e58e6ed1037831ea97dd58d9c0e76b8d is affected.
- Version 2.6.24 is affected.
- Before 2.6.24 is unaffected.
- Version 5.10.265, <= 5.10.* is unaffected.
- Version 5.15.216, <= 5.15.* is unaffected.
- Version 6.1.183, <= 6.1.* is unaffected.
- Version 6.6.152, <= 6.6.* is unaffected.
- Version 6.12.104, <= 6.12.* is unaffected.
- Version 6.18.45, <= 6.18.* is unaffected.
- Version 7.1.9, <= 7.1.* is unaffected.
- Version 7.2, <= * is unaffected.