CVE-2022-49892: In the Linux kernel, the following vulnerability has been resolved:  ftrace: Fix use-after-free for dynamic ftrace_ops  KASAN reported a use-after-free with ftrace ops [1]. It was found from vmcore that perf had registered two ops with the same content successively, both dynamic. After unregistering the second ops, a use-after-free occurred.  In ftrace_shutdown(), when the second ops is unregistered, the FTRACE_UPDATE_CALLS command is not set because there is another enabled ops with the same content.  Also, both ops are dynamic and the ftrace callback function is ftrace_ops_list_func, so the FTRACE_UPDATE_TRACE_FUNC command will not be set. Eventually the value of 'command' will be 0 and ftrace_shutdown() will skip the rcu synchronization.  However, ftrace may be activated. When the ops is released, another CPU may be accessing the ops.  Add the missing synchronization to fix this problem.  [1] BUG: KASAN: use-after-free in __ftrace_ops_list_func kernel/trace/ftrace.c:7020 [inline] BUG: KASAN: use-after-free in ftrace_ops_list_func+0x2b0/0x31c kernel/trace/ftrace.c:7049 Read of size 8 at addr ffff56551965bbc8 by task syz-executor.2/14468  CPU: 1 PID: 14468 Comm: syz-executor.2 Not tainted 5.10.0 #7 Hardware name: linux,dummy-virt (DT) Call trace:  dump_backtrace+0x0/0x40c arch/arm64/kernel/stacktrace.c:132  show_stack+0x30/0x40 arch/arm64/kernel/stacktrace.c:196  __dump_stack lib/dump_stack.c:77 [inline]  dump_stack+0x1b4/0x248 lib/dump_stack.c:118  print_address_description.constprop.0+0x28/0x48c mm/kasan/report.c:387  __kasan_report mm/kasan/report.c:547 [inline]  kasan_report+0x118/0x210 mm/kasan/report.c:564  check_memory_region_inline mm/kasan/generic.c:187 [inline]  __asan_load8+0x98/0xc0 mm/kasan/generic.c:253  __ftrace_ops_list_func kernel/trace/ftrace.c:7020 [inline]  ftrace_ops_list_func+0x2b0/0x31c kernel/trace/ftrace.c:7049  ftrace_graph_call+0x0/0x4  __might_sleep+0x8/0x100 include/linux/perf_event.h:1170  __might_fault mm/memory.c:5183 [inline]  __might_fault+0x58/0x70 mm/memory.c:5171  do_strncpy_from_user lib/strncpy_from_user.c:41 [inline]  strncpy_from_user+0x1f4/0x4b0 lib/strncpy_from_user.c:139  getname_flags+0xb0/0x31c fs/namei.c:149  getname+0x2c/0x40 fs/namei.c:209  [...]  Allocated by task 14445:  kasan_save_stack+0x24/0x50 mm/kasan/common.c:48  kasan_set_track mm/kasan/common.c:56 [inline]  __kasan_kmalloc mm/kasan/common.c:479 [inline]  __kasan_kmalloc.constprop.0+0x110/0x13c mm/kasan/common.c:449  kasan_kmalloc+0xc/0x14 mm/kasan/common.c:493  kmem_cache_alloc_trace+0x440/0x924 mm/slub.c:2950  kmalloc include/linux/slab.h:563 [inline]  kzalloc include/linux/slab.h:675 [inline]  perf_event_alloc.part.0+0xb4/0x1350 kernel/events/core.c:11230  perf_event_alloc kernel/events/core.c:11733 [inline]  __do_sys_perf_event_open kernel/events/core.c:11831 [inline]  __se_sys_perf_event_open+0x550/0x15f4 kernel/events/core.c:11723  __arm64_sys_perf_event_open+0x6c/0x80 kernel/events/core.c:11723  [...]  Freed by task 14445:  kasan_save_stack+0x24/0x50 mm/kasan/common.c:48  kasan_set_track+0x24/0x34 mm/kasan/common.c:56  kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:358  __kasan_slab_free.part.0+0x11c/0x1b0 mm/kasan/common.c:437  __kasan_slab_free mm/kasan/common.c:445 [inline]  kasan_slab_free+0x2c/0x40 mm/kasan/common.c:446  slab_free_hook mm/slub.c:1569 [inline]  slab_free_freelist_hook mm/slub.c:1608 [inline]  slab_free mm/slub.c:3179 [inline]  kfree+0x12c/0xc10 mm/slub.c:4176  perf_event_alloc.part.0+0xa0c/0x1350 kernel/events/core.c:11434  perf_event_alloc kernel/events/core.c:11733 [inline]  __do_sys_perf_event_open kernel/events/core.c:11831 [inline]  __se_sys_perf_event_open+0x550/0x15f4 kernel/events/core.c:11723  [...]