[FFmpeg-devel] [PATCH 2/4] cbs_mpeg2: Improve checks for invalid values

[Andreas Rheinhardt]

horizontal/vertical_size_value (containing the twelve least significant
bits of the frame size) mustn't be zero according to the specifications;
and the value 0 is forbidden for the colour_description elements.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
Given that xui is directly used in the syntax template, I had the
options a) to add xuir (as I did in my earlier attempt),
b) to change xui to accept ranges and change the syntax template (add
the ranges equaling "no custom range") or
c) change xui and add a new macro for what xui currently does.
I opted for c). The new macro is named xuib, b in analogy to your
proposal for cbs_h2645. Unfortunately, the naming of ui is inconsistent
with this, but changing this would basically touch every line in the
syntax template.
 libavcodec/cbs_mpeg2.c                 | 17 ++++++++++-------
 libavcodec/cbs_mpeg2_syntax_template.c | 24 ++++++++++++------------
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c
index cdde68ea38..4025812531 100644
--- a/libavcodec/cbs_mpeg2.c
+++ b/libavcodec/cbs_mpeg2.c
@@ -41,20 +41,23 @@
 #define SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]){ subs, __VA_ARGS__ }) : NULL)
 
 #define ui(width, name) \
-        xui(width, name, current->name, 0)
+        xuib(width, name, current->name, 0)
+#define uir(width, name, range_min, range_max) \
+        xui(width, name, current->name, range_min, range_max, 0)
 #define uis(width, name, subs, ...) \
-        xui(width, name, current->name, subs, __VA_ARGS__)
-
+        xuib(width, name, current->name, subs, __VA_ARGS__)
+#define xuib(width, name, var, subs, ...) \
+        xui(width, name, var, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
 
 #define READ
 #define READWRITE read
 #define RWContext GetBitContext
 
-#define xui(width, name, var, subs, ...) do { \
+#define xui(width, name, var, range_min, range_max, subs, ...) do { \
         uint32_t value = 0; \
         CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, \
                                    SUBSCRIPTS(subs, __VA_ARGS__), \
-                                   &value, 0, (1 << width) - 1)); \
+                                   &value, range_min, range_max)); \
         var = value; \
     } while (0)
 
@@ -81,10 +84,10 @@
 #define READWRITE write
 #define RWContext PutBitContext
 
-#define xui(width, name, var, subs, ...) do { \
+#define xui(width, name, var, range_min, range_max, subs, ...) do { \
         CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name, \
                                     SUBSCRIPTS(subs, __VA_ARGS__), \
-                                    var, 0, (1 << width) - 1)); \
+                                    var, range_min, range_max)); \
     } while (0)
 
 #define marker_bit() do { \
diff --git a/libavcodec/cbs_mpeg2_syntax_template.c b/libavcodec/cbs_mpeg2_syntax_template.c
index 10aaea7734..73bfeae29e 100644
--- a/libavcodec/cbs_mpeg2_syntax_template.c
+++ b/libavcodec/cbs_mpeg2_syntax_template.c
@@ -26,8 +26,8 @@ static int FUNC(sequence_header)(CodedBitstreamContext *ctx, RWContext *rw,
 
     ui(8,  sequence_header_code);
 
-    ui(12, horizontal_size_value);
-    ui(12, vertical_size_value);
+    uir(12, horizontal_size_value, 1, 4095);
+    uir(12, vertical_size_value,   1, 4095);
 
     mpeg2->horizontal_size = current->horizontal_size_value;
     mpeg2->vertical_size   = current->vertical_size_value;
@@ -79,7 +79,7 @@ static int FUNC(user_data)(CodedBitstreamContext *ctx, RWContext *rw,
 #endif
 
     for (k = 0; k < current->user_data_length; k++)
-        xui(8, user_data, current->user_data[k], 0);
+        xuib(8, user_data, current->user_data[k], 0);
 
     return 0;
 }
@@ -125,9 +125,9 @@ static int FUNC(sequence_display_extension)(CodedBitstreamContext *ctx, RWContex
 
     ui(1, colour_description);
     if (current->colour_description) {
-        ui(8, colour_primaries);
-        ui(8, transfer_characteristics);
-        ui(8, matrix_coefficients);
+        uir(8, colour_primaries,         1, 255);
+        uir(8, transfer_characteristics, 1, 255);
+        uir(8, matrix_coefficients,      1, 255);
     }
 
     ui(14, display_horizontal_size);
@@ -366,16 +366,16 @@ static int FUNC(slice_header)(CodedBitstreamContext *ctx, RWContext *rw,
                 if (!current->extra_information)
                     return AVERROR(ENOMEM);
                 for (k = 0; k < current->extra_information_length; k++) {
-                    xui(1, extra_bit_slice, bit, 0);
-                    xui(8, extra_information_slice[k],
-                        current->extra_information[k], 1, k);
+                    xuib(1, extra_bit_slice, bit, 0);
+                    xuib(8, extra_information_slice[k],
+                         current->extra_information[k], 1, k);
                 }
             }
 #else
             for (k = 0; k < current->extra_information_length; k++) {
-                xui(1, extra_bit_slice, 1, 0);
-                xui(8, extra_information_slice[k],
-                    current->extra_information[k], 1, k);
+                xuib(1, extra_bit_slice, 1, 0);
+                xuib(8, extra_information_slice[k],
+                     current->extra_information[k], 1, k);
             }
 #endif
         }
-- 
2.21.0