queue-4.19/tracing-use-strncpy-instead-of-memcpy-for-string-keys-in-hist-triggers.patch

   1 From 9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2 Mon Sep 17 00:00:00 2001
   2 From: Tom Zanussi <tom.zanussi@linux.intel.com>
   3 Date: Mon, 4 Feb 2019 15:07:24 -0600
   4 Subject: tracing: Use strncpy instead of memcpy for string keys in hist triggers
   5
   6 From: Tom Zanussi <tom.zanussi@linux.intel.com>
   7
   8 commit 9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2 upstream.
   9
  10 Because there may be random garbage beyond a string's null terminator,
  11 it's not correct to copy the the complete character array for use as a
  12 hist trigger key.  This results in multiple histogram entries for the
  13 'same' string key.
  14
  15 So, in the case of a string key, use strncpy instead of memcpy to
  16 avoid copying in the extra bytes.
  17
  18 Before, using the gdbus entries in the following hist trigger as an
  19 example:
  20
  21   # echo 'hist:key=comm' > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
  22   # cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist
  23
  24   ...
  25
  26   { comm: ImgDecoder #4                      } hitcount:        203
  27   { comm: gmain                              } hitcount:        213
  28   { comm: gmain                              } hitcount:        216
  29   { comm: StreamTrans #73                    } hitcount:        221
  30   { comm: mozStorage #3                      } hitcount:        230
  31   { comm: gdbus                              } hitcount:        233
  32   { comm: StyleThread#5                      } hitcount:        253
  33   { comm: gdbus                              } hitcount:        256
  34   { comm: gdbus                              } hitcount:        260
  35   { comm: StyleThread#4                      } hitcount:        271
  36
  37   ...
  38
  39   # cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
  40   51
  41
  42 After:
  43
  44   # cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
  45   1
  46
  47 Link: http://lkml.kernel.org/r/50c35ae1267d64eee975b8125e151e600071d4dc.1549309756.git.tom.zanussi@linux.intel.com
  48
  49 Cc: Namhyung Kim <namhyung@kernel.org>
  50 Cc: stable@vger.kernel.org
  51 Fixes: 79e577cbce4c4 ("tracing: Support string type key properly")
  52 Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
  53 Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
  54 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  55
  56 ---
  57  kernel/trace/trace_events_hist.c |    5 +++--
  58  1 file changed, 3 insertions(+), 2 deletions(-)
  59
  60 --- a/kernel/trace/trace_events_hist.c
  61 +++ b/kernel/trace/trace_events_hist.c
  62 @@ -4621,9 +4621,10 @@ static inline void add_to_key(char *comp
  63                 /* ensure NULL-termination */
  64                 if (size > key_field->size - 1)
  65                         size = key_field->size - 1;
  66 -       }
  67
  68 -       memcpy(compound_key + key_field->offset, key, size);
  69 +               strncpy(compound_key + key_field->offset, (char *)key, size);
  70 +       } else
  71 +               memcpy(compound_key + key_field->offset, key, size);
  72  }
  73
  74  static void