[tracker-miners] extract/mp3: Assert that the reader position is within mmap boundaries

[Carlos Garnacho <carlosg src gnome org>]

commit 2f3d04c16e61a0e5336c450ebaa50c4500078c14
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Aug 20 13:52:31 2017 +0200

    extract/mp3: Assert that the reader position is within mmap boundaries
    
    The 'pos' variable is always at the start of a frame, which means pos
    can't surpass the mmap size minus the frame size. This just happens
    implicitly, and is a programming error if we let that ever happen, so
    let's make it really sure this isn't possible.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=786539

 src/tracker-extract/tracker-extract-mp3.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-mp3.c b/src/tracker-extract/tracker-extract-mp3.c
index e89849c..3a59128 100644
--- a/src/tracker-extract/tracker-extract-mp3.c
+++ b/src/tracker-extract/tracker-extract-mp3.c
@@ -1888,6 +1888,8 @@ parse_id3v24 (const gchar           *data,
                size_t csize;
                unsigned short flags;
 
+               g_assert (pos <= size - frame_size);
+
                /* Frames are 10 bytes each and made up of:
                 *   Frame ID       $xx xx xx xx (4 chars)
                 *   Size           $xx xx xx xx
@@ -2090,6 +2092,8 @@ parse_id3v23 (const gchar          *data,
                size_t csize;
                unsigned short flags;
 
+               g_assert (pos <= size - frame_size);
+
                /* Frames are 10 bytes each and made up of:
                 *   Frame ID       $xx xx xx xx (4 chars)
                 *   Size           $xx xx xx xx
@@ -2226,6 +2230,8 @@ parse_id3v20 (const gchar          *data,
                id3v2frame frame;
                size_t csize;
 
+               g_assert (pos <= size - frame_size);
+
                if (pos + frame_size > tsize + header_size)  {
                        g_message ("[v20] Expected MP3 frame size (%d) to be within tag size (%d) boundaries, 
position = %d",
                                   frame_size,