ftrace: Fix removing of second function probe

When two function probes are added to set_ftrace_filter, and then one of
them is removed, the update to the function locations is not performed, and
the record keeping of the function states are corrupted, and causes an
ftrace_bug() to occur.

This is easily reproducable by adding two probes, removing one, and then
adding it back again.

 # cd /sys/kernel/debug/tracing
 # echo schedule:traceoff > set_ftrace_filter
 # echo do_IRQ:traceoff > set_ftrace_filter
 # echo \!do_IRQ:traceoff > /debug/tracing/set_ftrace_filter
 # echo do_IRQ:traceoff > set_ftrace_filter

Causes:
 ------------[ cut here ]------------
 WARNING: CPU: 2 PID: 1098 at kernel/trace/ftrace.c:2369 ftrace_get_addr_curr+0x143/0x220
 Modules linked in: [...]
 CPU: 2 PID: 1098 Comm: bash Not tainted 4.10.0-test+ #405
 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
 Call Trace:
  dump_stack+0x68/0x9f
  __warn+0x111/0x130
  ? trace_irq_work_interrupt+0xa0/0xa0
  warn_slowpath_null+0x1d/0x20
  ftrace_get_addr_curr+0x143/0x220
  ? __fentry__+0x10/0x10
  ftrace_replace_code+0xe3/0x4f0
  ? ftrace_int3_handler+0x90/0x90
  ? printk+0x99/0xb5
  ? 0xffffffff81000000
  ftrace_modify_all_code+0x97/0x110
  arch_ftrace_update_code+0x10/0x20
  ftrace_run_update_code+0x1c/0x60
  ftrace_run_modify_code.isra.48.constprop.62+0x8e/0xd0
  register_ftrace_function_probe+0x4b6/0x590
  ? ftrace_startup+0x310/0x310
  ? debug_lockdep_rcu_enabled.part.4+0x1a/0x30
  ? update_stack_state+0x88/0x110
  ? ftrace_regex_write.isra.43.part.44+0x1d3/0x320
  ? preempt_count_sub+0x18/0xd0
  ? mutex_lock_nested+0x104/0x800
  ? ftrace_regex_write.isra.43.part.44+0x1d3/0x320
  ? __unwind_start+0x1c0/0x1c0
  ? _mutex_lock_nest_lock+0x800/0x800
  ftrace_trace_probe_callback.isra.3+0xc0/0x130
  ? func_set_flag+0xe0/0xe0
  ? __lock_acquire+0x642/0x1790
  ? __might_fault+0x1e/0x20
  ? trace_get_user+0x398/0x470
  ? strcmp+0x35/0x60
  ftrace_trace_onoff_callback+0x48/0x70
  ftrace_regex_write.isra.43.part.44+0x251/0x320
  ? match_records+0x420/0x420
  ftrace_filter_write+0x2b/0x30
  __vfs_write+0xd7/0x330
  ? do_loop_readv_writev+0x120/0x120
  ? locks_remove_posix+0x90/0x2f0
  ? do_lock_file_wait+0x160/0x160
  ? __lock_is_held+0x93/0x100
  ? rcu_read_lock_sched_held+0x5c/0xb0
  ? preempt_count_sub+0x18/0xd0
  ? __sb_start_write+0x10a/0x230
  ? vfs_write+0x222/0x240
  vfs_write+0xef/0x240
  SyS_write+0xab/0x130
  ? SyS_read+0x130/0x130
  ? trace_hardirqs_on_caller+0x182/0x280
  ? trace_hardirqs_on_thunk+0x1a/0x1c
  entry_SYSCALL_64_fastpath+0x18/0xad
 RIP: 0033:0x7fe61c157c30
 RSP: 002b:00007ffe87890258 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
 RAX: ffffffffffffffda RBX: ffffffff8114a410 RCX: 00007fe61c157c30
 RDX: 0000000000000010 RSI: 000055814798f5e0 RDI: 0000000000000001
 RBP: ffff8800c9027f98 R08: 00007fe61c422740 R09: 00007fe61ca53700
 R10: 0000000000000073 R11: 0000000000000246 R12: 0000558147a36400
 R13: 00007ffe8788f160 R14: 0000000000000024 R15: 00007ffe8788f15c
  ? trace_hardirqs_off_caller+0xc0/0x110
 ---[ end trace 99fa09b3d9869c2c ]---
 Bad trampoline accounting at: ffffffff81cc3b00 (do_IRQ+0x0/0x150)

Cc: stable@vger.kernel.org
Fixes: 59df055f1991 ("ftrace: trace different functions with a different tracer")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 16 insertions, 4 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 34f63e78d661..4b6459a57fbc 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3780,23 +3780,24 @@ static void __enable_ftrace_function_probe(struct ftrace_ops_hash *old_hash)
         ftrace_probe_registered = 1;
 }
 
-static void __disable_ftrace_function_probe(void)
+static bool __disable_ftrace_function_probe(void)
 {
         int i;
 
         if (!ftrace_probe_registered)
-                return;
+                return false;
 
         for (i = 0; i < FTRACE_FUNC_HASHSIZE; i++) {
                 struct hlist_head *hhd = &ftrace_func_hash[i];
                 if (hhd->first)
-                        return;
+                        return false;
         }
 
         /* no more funcs left */
         ftrace_shutdown(&trace_probe_ops, 0);
 
         ftrace_probe_registered = 0;
+        return true;
 }
 
 
@@ -3926,6 +3927,7 @@ static void
 __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                                   void *data, int flags)
 {
+        struct ftrace_ops_hash old_hash_ops;
         struct ftrace_func_entry *rec_entry;
         struct ftrace_func_probe *entry;
         struct ftrace_func_probe *p;
@@ -3937,6 +3939,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         struct hlist_node *tmp;
         char str[KSYM_SYMBOL_LEN];
         int i, ret;
+        bool disabled;
 
         if (glob && (strcmp(glob, "*") == 0 || !strlen(glob)))
                 func_g.search = NULL;
@@ -3955,6 +3958,10 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 
         mutex_lock(&trace_probe_ops.func_hash->regex_lock);
 
+        old_hash_ops.filter_hash = old_hash;
+        /* Probes only have filters */
+        old_hash_ops.notrace_hash = NULL;
+
         hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
         if (!hash)
                 /* Hmm, should report this somehow */
@@ -3992,12 +3999,17 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                 }
         }
         mutex_lock(&ftrace_lock);
-        __disable_ftrace_function_probe();
+        disabled = __disable_ftrace_function_probe();
         /*
          * Remove after the disable is called. Otherwise, if the last
          * probe is removed, a null hash means *all enabled*.
          */
         ret = ftrace_hash_move(&trace_probe_ops, 1, orig_hash, hash);
+
+        /* still need to update the function call sites */
+        if (ftrace_enabled && !disabled)
+                ftrace_run_modify_code(&trace_probe_ops, FTRACE_UPDATE_CALLS,
+                                       &old_hash_ops);
         synchronize_sched();
         if (!ret)
                 free_ftrace_hash_rcu(old_hash);