CVE-2024-36979

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> net: bridge: mst: fix vlan use-after-free<br /> <br /> syzbot reported a suspicious rcu usage[1] in bridge&amp;#39;s mst code. While<br /> fixing it I noticed that nothing prevents a vlan to be freed while<br /> walking the list from the same path (br forward delay timer). Fix the rcu<br /> usage and also make sure we are not accessing freed memory by making<br /> br_mst_vlan_set_state use rcu read lock.<br /> <br /> [1]<br /> WARNING: suspicious RCU usage<br /> 6.9.0-rc6-syzkaller #0 Not tainted<br /> -----------------------------<br /> net/bridge/br_private.h:1599 suspicious rcu_dereference_protected() usage!<br /> ...<br /> stack backtrace:<br /> CPU: 1 PID: 8017 Comm: syz-executor.1 Not tainted 6.9.0-rc6-syzkaller #0<br /> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024<br /> Call Trace:<br /> <br /> __dump_stack lib/dump_stack.c:88 [inline]<br /> dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114<br /> lockdep_rcu_suspicious+0x221/0x340 kernel/locking/lockdep.c:6712<br /> nbp_vlan_group net/bridge/br_private.h:1599 [inline]<br /> br_mst_set_state+0x1ea/0x650 net/bridge/br_mst.c:105<br /> br_set_state+0x28a/0x7b0 net/bridge/br_stp.c:47<br /> br_forward_delay_timer_expired+0x176/0x440 net/bridge/br_stp_timer.c:88<br /> call_timer_fn+0x18e/0x650 kernel/time/timer.c:1793<br /> expire_timers kernel/time/timer.c:1844 [inline]<br /> __run_timers kernel/time/timer.c:2418 [inline]<br /> __run_timer_base+0x66a/0x8e0 kernel/time/timer.c:2429<br /> run_timer_base kernel/time/timer.c:2438 [inline]<br /> run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2448<br /> __do_softirq+0x2c6/0x980 kernel/softirq.c:554<br /> invoke_softirq kernel/softirq.c:428 [inline]<br /> __irq_exit_rcu+0xf2/0x1c0 kernel/softirq.c:633<br /> irq_exit_rcu+0x9/0x30 kernel/softirq.c:645<br /> instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]<br /> sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043<br /> <br /> <br /> asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702<br /> RIP: 0010:lock_acquire+0x264/0x550 kernel/locking/lockdep.c:5758<br /> Code: 2b 00 74 08 4c 89 f7 e8 ba d1 84 00 f6 44 24 61 02 0f 85 85 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25<br /> RSP: 0018:ffffc90013657100 EFLAGS: 00000206<br /> RAX: 0000000000000001 RBX: 1ffff920026cae2c RCX: 0000000000000001<br /> RDX: dffffc0000000000 RSI: ffffffff8bcaca00 RDI: ffffffff8c1eaa60<br /> RBP: ffffc90013657260 R08: ffffffff92efe507 R09: 1ffffffff25dfca0<br /> R10: dffffc0000000000 R11: fffffbfff25dfca1 R12: 1ffff920026cae28<br /> R13: dffffc0000000000 R14: ffffc90013657160 R15: 0000000000000246