releases/4.14.130/tracing-silence-gcc-9-array-bounds-warning.patch

   1 From 0c97bf863efce63d6ab7971dad811601e6171d2f Mon Sep 17 00:00:00 2001
   2 From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
   3 Date: Thu, 23 May 2019 14:45:35 +0200
   4 Subject: tracing: Silence GCC 9 array bounds warning
   5
   6 From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
   7
   8 commit 0c97bf863efce63d6ab7971dad811601e6171d2f upstream.
   9
  10 Starting with GCC 9, -Warray-bounds detects cases when memset is called
  11 starting on a member of a struct but the size to be cleared ends up
  12 writing over further members.
  13
  14 Such a call happens in the trace code to clear, at once, all members
  15 after and including `seq` on struct trace_iterator:
  16
  17     In function 'memset',
  18         inlined from 'ftrace_dump' at kernel/trace/trace.c:8914:3:
  19     ./include/linux/string.h:344:9: warning: '__builtin_memset' offset
  20     [8505, 8560] from the object at 'iter' is out of the bounds of
  21     referenced subobject 'seq' with type 'struct trace_seq' at offset
  22     4368 [-Warray-bounds]
  23       344 |  return __builtin_memset(p, c, size);
  24           |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
  25
  26 In order to avoid GCC complaining about it, we compute the address
  27 ourselves by adding the offsetof distance instead of referring
  28 directly to the member.
  29
  30 Since there are two places doing this clear (trace.c and trace_kdb.c),
  31 take the chance to move the workaround into a single place in
  32 the internal header.
  33
  34 Link: http://lkml.kernel.org/r/20190523124535.GA12931@gmail.com
  35
  36 Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
  37 [ Removed unnecessary parenthesis around "iter" ]
  38 Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
  39 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  40
  41 ---
  42  kernel/trace/trace.c     |    6 +-----
  43  kernel/trace/trace.h     |   18 ++++++++++++++++++
  44  kernel/trace/trace_kdb.c |    6 +-----
  45  3 files changed, 20 insertions(+), 10 deletions(-)
  46
  47 --- a/kernel/trace/trace.c
  48 +++ b/kernel/trace/trace.c
  49 @@ -8249,12 +8249,8 @@ void ftrace_dump(enum ftrace_dump_mode o
  50
  51                 cnt++;
  52
  53 -               /* reset all but tr, trace, and overruns */
  54 -               memset(&iter.seq, 0,
  55 -                      sizeof(struct trace_iterator) -
  56 -                      offsetof(struct trace_iterator, seq));
  57 +               trace_iterator_reset(&iter);
  58                 iter.iter_flags |= TRACE_FILE_LAT_FMT;
  59 -               iter.pos = -1;
  60
  61                 if (trace_find_next_entry_inc(&iter) != NULL) {
  62                         int ret;
  63 --- a/kernel/trace/trace.h
  64 +++ b/kernel/trace/trace.h
  65 @@ -1871,4 +1871,22 @@ static inline int tracing_alloc_snapshot
  66
  67  extern struct trace_iterator *tracepoint_print_iter;
  68
  69 +/*
  70 + * Reset the state of the trace_iterator so that it can read consumed data.
  71 + * Normally, the trace_iterator is used for reading the data when it is not
  72 + * consumed, and must retain state.
  73 + */
  74 +static __always_inline void trace_iterator_reset(struct trace_iterator *iter)
  75 +{
  76 +       const size_t offset = offsetof(struct trace_iterator, seq);
  77 +
  78 +       /*
  79 +        * Keep gcc from complaining about overwriting more than just one
  80 +        * member in the structure.
  81 +        */
  82 +       memset((char *)iter + offset, 0, sizeof(struct trace_iterator) - offset);
  83 +
  84 +       iter->pos = -1;
  85 +}
  86 +
  87  #endif /* _LINUX_KERNEL_TRACE_H */
  88 --- a/kernel/trace/trace_kdb.c
  89 +++ b/kernel/trace/trace_kdb.c
  90 @@ -41,12 +41,8 @@ static void ftrace_dump_buf(int skip_lin
  91
  92         kdb_printf("Dumping ftrace buffer:\n");
  93
  94 -       /* reset all but tr, trace, and overruns */
  95 -       memset(&iter.seq, 0,
  96 -                  sizeof(struct trace_iterator) -
  97 -                  offsetof(struct trace_iterator, seq));
  98 +       trace_iterator_reset(&iter);
  99         iter.iter_flags |= TRACE_FILE_LAT_FMT;
 100 -       iter.pos = -1;
 101
 102         if (cpu_file == RING_BUFFER_ALL_CPUS) {
 103                 for_each_tracing_cpu(cpu) {