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tracing: Fix kernel crash while using empty filter with perf 

Kernel is crashing when user tries to record 'ftrace:function' event
with empty filter:

  # perf record -e ftrace:function --filter="" ls

  # dmesg
  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  Oops: 0000 [#1] SMP PTI
  ...
  RIP: 0010:ftrace_profile_set_filter+0x14b/0x2d0
  RSP: 0018:ffffa4a7c0da7d20 EFLAGS: 00010246
  RAX: ffffa4a7c0da7d64 RBX: 0000000000000000 RCX: 0000000000000006
  RDX: 0000000000000000 RSI: 0000000000000092 RDI: ffff8c48ffc968f0
  ...
  Call Trace:
   _perf_ioctl+0x54a/0x6b0
   ? rcu_all_qs+0x5/0x30
  ...

After patch:
  # perf record -e ftrace:function --filter="" ls
  failed to set filter "" on event ftrace:function with 22 (Invalid argument)

Also, if user tries to echo "" > filter, it used to throw an error.
This behavior got changed by commit 80765597bc ("tracing: Rewrite
filter logic to be simpler and faster"). This patch restores the
behavior as a side effect:

Before patch:
  # echo "" > filter
  #

After patch:
  # echo "" > filter
  bash: echo: write error: Invalid argument
  #

Link: http://lkml.kernel.org/r/20180420150758.19787-1-ravi.bangoria@linux.ibm.com

Fixes: 80765597bc ("tracing: Rewrite filter logic to be simpler and faster")
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Ravi Bangoria 2018-04-20 20:37:58 +05:30 committed by Steven Rostedt (VMware)
parent 1c758a2202
commit ba16293dad
1 changed files with 7 additions and 7 deletions
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14
kernel/trace/trace_events_filter.c
View File

@ -1499,14 +1499,14 @@ static int process_preds(struct trace_event_call *call,
return ret;
}
if (!nr_preds) {
prog = NULL;
} else {
prog = predicate_parse(filter_string, nr_parens, nr_preds,
if (!nr_preds)
return -EINVAL;
prog = predicate_parse(filter_string, nr_parens, nr_preds,
parse_pred, call, pe);
if (IS_ERR(prog))
return PTR_ERR(prog);
}
if (IS_ERR(prog))
return PTR_ERR(prog);
rcu_assign_pointer(filter->prog, prog);
return 0;
}