Vulnerabilidad en kernel de Linux (CVE-2024-50126)

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: sched: usar la sección crítica del lado de lectura de RCU en taprio_dump(). Corrija el posible use-after-free en 'taprio_dump()' agregando allí la sección crítica del lado de lectura de RCU. Nunca visto en x86 pero encontrado en un sistema arm64 habilitado para KASAN al investigar https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa: [T15862] ERROR: KASAN: slab-use-after-free en taprio_dump+0xa0c/0xbb0 [T15862] Lectura de tamaño 4 en la dirección ffff0000d4bb88f8 por la tarea repro/15862 [T15862] [T15862] CPU: 0 UID: 0 PID: 15862 Comm: repro No contaminado 6.11.0-rc1-00293-gdefaf1a2113a-dirty #2 [T15862] Nombre del hardware: QEMU QEMU Virtual Machine, BIOS edk2-20240524-5.fc40 24/05/2024 [T15862] Seguimiento de llamadas: [T15862] dump_backtrace+0x20c/0x220 [T15862] show_stack+0x2c/0x40 [T15862] dump_stack_lvl+0xf8/0x174 [T15862] print_report+0x170/0x4d8 [T15862] kasan_report+0xb8/0x1d4 [T15862] __asan_report_load4_noabort+0x20/0x2c [T15862] taprio_dump+0xa0c/0xbb0 [T15862] El comando tc_fill_qdisc_notify.isra.0_0x330_0x3a0_tc_modify_qdisc_0x7b8_0x1838_rtnetlink_rcv_msg_0x3c8_0xc20_netlink_rcv_skb_0x1f8_0x3d4_rtnetlink_rcv_0x28_0x40_netlink_unicast_0x51c_0x790_netlink_sendmsg_0x79c_0xc20_tc_sendmsg_0x1a ... [T15862] ____sys_sendmsg+0x6c0/0x840 [T15862] ___sys_sendmsg+0x1ac/0x1f0 [T15862] __sys_sendmsg+0x110/0x1d0 [T15862] __arm64_sys_sendmsg+0x74/0xb0 [T15862] invoke_syscall+0x88/0x2e0 [T15862] el0_svc_common.constprop.0+0xe4/0x2a0 [T15862] do_el0_svc+0x44/0x60 [T15862] el0_svc+0x50/0x184 [T15862] el0t_64_sync_handler+0x120/0x12c [T15862] el0t_64_sync+0x190/0x194 [T15862] [T15862] Asignado por la tarea 15857: [T15862] kasan_save_stack+0x3c/0x70 [T15862] kasan_save_track+0x20/0x3c [T15862] kasan_save_alloc_info+0x40/0x60 [T15862] __kasan_kmalloc+0xd4/0xe0 [T15862] __kmalloc_cache_noprof+0x194/0x334 [T15862] taprio_change+0x45c/0x2fe0 [T15862] tc_modify_qdisc+0x6a8/0x1838 [T15862] rtnetlink_rcv_msg+0x3c8/0xc20 [T15862] netlink_rcv_skb+0x1f8/0x3d4 [T15862] rtnetlink_rcv+0x28/0x40 [T15862] netlink_unicast+0x51c/0x790 [T15862] netlink_sendmsg+0x79c/0xc20 [T15862] __sock_sendmsg+0xe0/0x1a0 [T15862] ____sys_sendmsg+0x6c0/0x840 [T15862] ___sys_sendmsg+0x1ac/0x1f0 [T15862] __sys_sendmsg+0x110/0x1d0 [T15862] __arm64_sys_sendmsg+0x74/0xb0 [T15862] invoke_syscall+0x88/0x2e0 [T15862] el0_svc_common.constprop.0+0xe4/0x2a0 [T15862] do_el0_svc+0x44/0x60 [T15862] el0_svc+0x50/0x184 [T15862] el0t_64_sync_handler+0x120/0x12c [T15862] el0t_64_sync+0x190/0x194 [T15862] [T15862] Liberado por la tarea 6192: [T15862] kasan_save_stack+0x3c/0x70 [T15862] kasan_save_track+0x20/0x3c [T15862] kasan_save_free_info+0x4c/0x80 [T15862] poison_slab_object+0x110/0x160 [T15862] __kasan_slab_free+0x3c/0x74 [T15862] kfree+0x134/0x3c0 [T15862] taprio_free_sched_cb+0x18c/0x220 [T15862] rcu_core+0x920/0x1b7c [T15862] rcu_core_si+0x10/0x1c [T15862] handle_softirqs+0x2e8/0xd64 [T15862] __do_softirq+0x14/0x20