CVE-2024-35892

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: net/sched: corrige lockdep splat en qdisc_tree_reduce_backlog() qdisc_tree_reduce_backlog() se llama con el bloqueo de qdisc retenido, no con RTNL. Debemos usar qdisc_lookup_rcu() en lugar de qdisc_lookup() syzbot informó: ADVERTENCIA: uso sospechoso de RCU 6.1.74-syzkaller #0 No contaminado ---------------------- ------- ¡net/sched/sch_api.c:305 uso sospechoso de rcu_dereference_protected()! otra información que podría ayudarnos a depurar esto: rcu_scheduler_active = 2, debug_locks = 1 3 bloqueos mantenidos por udevd/1142: #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, en: rcu_lock_acquire include/linux /rcupdate.h:306 [en línea] #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, en: rcu_read_lock include/linux/rcupdate.h:747 [en línea] #0: ffffffff87c729a0 (rcu_read_lock ){....}-{1:2}, en: net_tx_action+0x64a/0x970 net/core/dev.c:5282 #1: ffff888171861108 (&sch->q.lock){+.-.}-{ 2:2}, en: spin_lock include/linux/spinlock.h:350 [en línea] #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, en: net_tx_action+0x754 /0x970 net/core/dev.c:5297 #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, en: rcu_lock_acquire include/linux/rcupdate.h:306 [en línea] #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, en: rcu_read_lock include/linux/rcupdate.h:747 [en línea] #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2} , en: qdisc_tree_reduce_backlog+0x84/0x580 net/sched/sch_api.c:792 stack backtrace: CPU: 1 PID: 1142 Comm: udevd Not tainted 6.1.74-syzkaller #0 Nombre del hardware: Google Google Compute Engine/Google Compute Engine, BIOS Google 25/01/2024 Seguimiento de llamadas: [] __dump_stack lib/dump_stack.c:88 [en línea] [] dump_stack_lvl+0x1b1/0x28f lib/dump_stack.c:106 [ ] dump_stack+0x15/0x1e lib/dump_stack.c:113 [] lockdep_rcu_suspicious+0x1b9/0x260 kernel/locking/lockdep.c:6592 [] qdisc_lookup+0xac/0x6f0 net/sched/sch_a foto.c: 305 [] qdisc_tree_reduce_backlog+0x243/0x580 net/sched/sch_api.c:811 [] pfifo_tail_enqueue+0x32c/0x4b0 net/sched/sch_fifo.c:51 [ ] qdisc_enqueue incluye/net/sch_generic .h:833 [en línea] [] netem_dequeue+0xeb3/0x15d0 net/sched/sch_netem.c:723 [] dequeue_skb net/sched/sch_generic.c:292 [en línea] [] qdisc_restart net/sched/sch_generic.c:397 [en línea] [] __qdisc_run+0x249/0x1e60 net/sched/sch_generic.c:415 [] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125 [] net_tx_action+0x7c9/0x970 net/core/dev.c:5313 [] __do_softirq+0x2bd/0x9bd kernel/softirq.c:616 [] invoke_softirq kernel/softirq.c: 447 [ en línea] [] __irq_exit_rcu+0xca/0x230 kernel/softirq.c:700 [] irq_exit_rcu+0x9/0x20 kernel/softirq.c:712 [] sysvec_apic_timer_interrupt+0 x42/0x90 arco/x86/ kernel/apic/apic.c:1107 [] asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:656

CVE-2024-35892 is a vulnerability in the Linux kernel’s network scheduler caused by improper use of the qdisc_lookup() function. This function assumes the global RTNL lock is held, but in the qdisc_tree_reduce_backlog() function, only a local queue lock is used. This mismatch creates a race condition that could lead to system instability or crashes. The issue has been fixed by replacing qdisc_lookup() with an RCU-safe version that works correctly in this context.