trace-cmd: Add check for truncated files

If the trace data file that is being read is truncated, mmap'ing its
non-existent page does not give any error. When the page is read, the
process dies with a SIGBUS.

This patch adds a file size check while initializing the trace data and
makes sure that the file size matches the expected size; otherwise an
error is returned.

Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Link: http://lkml.kernel.org/r/1308615578-556-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/trace-input.c b/trace-input.c
index f537ef5..723d47f 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -92,6 +92,7 @@ struct tracecmd_input {
         size_t                  header_files_start;
         size_t                  ftrace_files_start;
         size_t                  event_files_start;
+        size_t                  total_file_size;
 };
 
 __thread struct tracecmd_input *tracecmd_curr_thread_handle;
@@ -2085,6 +2086,15 @@ int tracecmd_init_data(struct tracecmd_input *handle)
                 handle->cpu_data[cpu].file_offset = offset;
                 handle->cpu_data[cpu].file_size = size;
 
+                if (offset + size > handle->total_file_size) {
+                        /* this happens if the file got truncated */
+                        printf("File possibly truncated. "
+                                "Need at least %llu, but file size is %lu.\n",
+                                offset + size, handle->total_file_size);
+                        errno = EINVAL;
+                        return -1;
+                }
+
                 if (init_cpu(handle, cpu))
                         return -1;
         }
@@ -2189,6 +2199,12 @@ struct tracecmd_input *tracecmd_alloc_fd(int fd)
         handle->header_files_start =
                 lseek64(handle->fd, 0, SEEK_CUR);
 
+        handle->total_file_size =
+                lseek64(handle->fd, 0, SEEK_END);
+
+        handle->header_files_start =
+                lseek64(handle->fd, handle->header_files_start, SEEK_SET);
+
         return handle;
 
  failed_read: