From 86b389ff22bd6ad8fd3cb98e41cd271886c6d023 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Sun, 27 May 2018 20:54:44 -0400 Subject: tracing: Fix crash when freeing instances with event triggers If a instance has an event trigger enabled when it is freed, it could cause an access of free memory. Here's the case that crashes: # cd /sys/kernel/tracing # mkdir instances/foo # echo snapshot > instances/foo/events/initcall/initcall_start/trigger # rmdir instances/foo Would produce: general protection fault: 0000 [#1] PREEMPT SMP PTI Modules linked in: tun bridge ... CPU: 5 PID: 6203 Comm: rmdir Tainted: G W 4.17.0-rc4-test+ #933 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 RIP: 0010:clear_event_triggers+0x3b/0x70 RSP: 0018:ffffc90003783de0 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 6b6b6b6b6b6b6b2b RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8800c7130ba0 RBP: ffffc90003783e00 R08: ffff8801131993f8 R09: 0000000100230016 R10: ffffc90003783d80 R11: 0000000000000000 R12: ffff8800c7130ba0 R13: ffff8800c7130bd8 R14: ffff8800cc093768 R15: 00000000ffffff9c FS: 00007f6f4aa86700(0000) GS:ffff88011eb40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f6f4a5aed60 CR3: 00000000cd552001 CR4: 00000000001606e0 Call Trace: event_trace_del_tracer+0x2a/0xc5 instance_rmdir+0x15c/0x200 tracefs_syscall_rmdir+0x52/0x90 vfs_rmdir+0xdb/0x160 do_rmdir+0x16d/0x1c0 __x64_sys_rmdir+0x17/0x20 do_syscall_64+0x55/0x1a0 entry_SYSCALL_64_after_hwframe+0x49/0xbe This was due to the call the clears out the triggers when an instance is being deleted not removing the trigger from the link list. Cc: stable@vger.kernel.org Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework") Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_trigger.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'kernel/trace/trace_events_trigger.c') diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index d251cabcf69a..9be317d388c5 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -483,9 +483,10 @@ clear_event_triggers(struct trace_array *tr) struct trace_event_file *file; list_for_each_entry(file, &tr->events, list) { - struct event_trigger_data *data; - list_for_each_entry_rcu(data, &file->triggers, list) { + struct event_trigger_data *data, *n; + list_for_each_entry_safe(data, n, &file->triggers, list) { trace_event_trigger_enable_disable(file, 0); + list_del_rcu(&data->list); if (data->ops->free) data->ops->free(data->ops, data); } -- cgit v1.2.3 From 2824f5033248600673e3e126a4d135363cbfd9ac Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Mon, 28 May 2018 10:56:36 -0400 Subject: tracing: Make the snapshot trigger work with instances The snapshot trigger currently only affects the main ring buffer, even when it is used by the instances. This can be confusing as the snapshot trigger is listed in the instance. > # cd /sys/kernel/tracing > # mkdir instances/foo > # echo snapshot > instances/foo/events/syscalls/sys_enter_fchownat/trigger > # echo top buffer > trace_marker > # echo foo buffer > instances/foo/trace_marker > # touch /tmp/bar > # chown rostedt /tmp/bar > # cat instances/foo/snapshot # tracer: nop # # # * Snapshot is freed * # # Snapshot commands: # echo 0 > snapshot : Clears and frees snapshot buffer # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated. # Takes a snapshot of the main buffer. # echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free) # (Doesn't have to be '2' works with any number that # is not a '0' or '1') > # cat snapshot # tracer: nop # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | bash-1189 [000] .... 111.488323: tracing_mark_write: top buffer Not only did the snapshot occur in the top level buffer, but the instance snapshot buffer should have been allocated, and it is still free. Cc: stable@vger.kernel.org Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework") Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_trigger.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'kernel/trace/trace_events_trigger.c') diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index 9be317d388c5..8b5bdcf64871 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -643,6 +643,7 @@ event_trigger_callback(struct event_command *cmd_ops, trigger_data->count = -1; trigger_data->ops = trigger_ops; trigger_data->cmd_ops = cmd_ops; + trigger_data->private_data = file; INIT_LIST_HEAD(&trigger_data->list); INIT_LIST_HEAD(&trigger_data->named_list); @@ -1054,7 +1055,12 @@ static void snapshot_trigger(struct event_trigger_data *data, void *rec, struct ring_buffer_event *event) { - tracing_snapshot(); + struct trace_event_file *file = data->private_data; + + if (file) + tracing_snapshot_instance(file->tr); + else + tracing_snapshot(); } static void @@ -1077,7 +1083,7 @@ register_snapshot_trigger(char *glob, struct event_trigger_ops *ops, { int ret = register_trigger(glob, ops, data, file); - if (ret > 0 && tracing_alloc_snapshot() != 0) { + if (ret > 0 && tracing_alloc_snapshot_instance(file->tr) != 0) { unregister_trigger(glob, ops, data, file); ret = 0; } -- cgit v1.2.3