trace-cmd: Don't try to read unmapped memory (v2).

Under some circumstances, I'm not sure exactly which, a trace.dat file
may contain a bunch of zeros at the end of one or more of the trace
logs.  This can lead to tracecmd_peek_data() attempting to read past
the end of the mmaped log, causing SIGSEGV.

This is a two part fix.

1) For 'new format' data, we always try to read 8 bytes of data.  Make
sure that they are all on the current page.

2) In pevent_print_event(), if record->size is negative, warn and then
skip attempting to print it.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
LKML-Reference: <1279586810-29859-2-git-send-email-ddaney@caviumnetworks.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 7 insertions, 1 deletions

diff --git a/parse-events.c b/parse-events.c
index 9d5a3fa..1e854e2 100644
--- a/parse-events.c
+++ b/parse-events.c
@@ -3881,6 +3881,11 @@ void pevent_print_event(struct pevent *pevent, struct trace_seq *s,
         usecs = record->ts - secs * NSECS_PER_SEC;
         usecs = (usecs + 500) / NSECS_PER_USEC;
 
+        if (record->size < 0) {
+                do_warning("ug! negative record size %d", record->size);
+                return;
+        }
+
         type = trace_parse_common_type(pevent, data);
 
         event = pevent_find_event(pevent, type);
diff --git a/trace-input.c b/trace-input.c
index b3dbca3..7db5577 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -1513,7 +1513,8 @@ read_again:
         if (index < 0)
                 die("negative index on cpu record %d", cpu);
 
-        if (index >= handle->cpu_data[cpu].page_size + pevent->header_page_data_offset) {
+        if (index + (pevent->old_format ? 0 : 4) >=
+            handle->cpu_data[cpu].page_size + pevent->header_page_data_offset) {
                 if (get_next_page(handle, cpu))
                         return NULL;
                 return tracecmd_peek_data(handle, cpu);