extmod/modframebuf: Fix FrameBuffer size check for stride corner-cases.

This is a fix for issue micropython#15944, and handles corner cases in the FrameBuffer
code when using stride values where the last line's stride may extend past
the end of the underlying buffer.  This commit includes extra tests for
these corner cases.

For example a GS8 format FrameBuffer with a width of 8, height of 2 and
stride of 10 should be able to fit into a buffer of size 18 (10 bytes for
the first horizontal line, and 8 bytes for the second -- the full 10 bytes
are not needed).

Similarly a 1 by 9 FrameBuffer in MONO_VLSB format with a stride of 10
should be able to fit into a buffer of length 11 (10 bytes for the first
8 lines, and then one byte for the 9th line.

Being able to do this is particularly important when cropping the corner of
an existing FrameBuffer, either to copy a sprite or to clip drawing.

Signed-off-by: Corran Webster <[email protected]>

Author: corranwebster

extmod/modframebuf.c

@@ -282,23 +282,29 @@ static mp_obj_t framebuf_make_new(const mp_obj_type_t *type, size_t n_args, size
         mp_raise_ValueError(NULL);
     }
 
-    size_t height_required = height;
     size_t bpp = 1;
+    size_t height_required = height;
+    size_t width_required = width;
+    size_t strides_required = height - 1;
 
     switch (format) {
         case FRAMEBUF_MVLSB:
             height_required = (height + 7) & ~7;
+            strides_required = height_required - 8;
             break;
         case FRAMEBUF_MHLSB:
         case FRAMEBUF_MHMSB:
             stride = (stride + 7) & ~7;
+            width_required = (width + 7) & ~7;
             break;
         case FRAMEBUF_GS2_HMSB:
             stride = (stride + 3) & ~3;
+            width_required = (width + 3) & ~3;
             bpp = 2;
             break;
         case FRAMEBUF_GS4_HMSB:
             stride = (stride + 1) & ~1;
+            width_required = (width + 1) & ~1;
             bpp = 4;
             break;
         case FRAMEBUF_GS8:
@@ -314,7 +320,7 @@ static mp_obj_t framebuf_make_new(const mp_obj_type_t *type, size_t n_args, size
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args_in[0], &bufinfo, MP_BUFFER_WRITE);
 
-    if (height_required * stride * bpp / 8 > bufinfo.len) {
+    if ((strides_required * stride + (height_required - strides_required) * width_required) * bpp / 8 > bufinfo.len) {
         mp_raise_ValueError(NULL);
     }
 

tests/extmod/framebuf_bounds.py

@@ -21,11 +21,25 @@ def test_constructor(*args):
 test_constructor(bytearray(20), 10, 10, framebuf.MONO_HLSB, 10)
 test_constructor(bytearray(20), 10, 10, framebuf.MONO_HLSB, 9)
 test_constructor(bytearray(20), 10, 10, framebuf.MONO_HLSB, -1)
+test_constructor(bytearray(20), 10, 10, framebuf.MONO_HLSB, 16)
+test_constructor(bytearray(20), 10, 10, framebuf.MONO_HLSB, 17)
+test_constructor(bytearray(19), 8, 10, framebuf.MONO_HLSB, 16)
+test_constructor(bytearray(18), 8, 10, framebuf.MONO_HLSB, 9)
+test_constructor(bytearray(19), 8, 10, framebuf.MONO_HLSB, 16)
 
 print(framebuf.MONO_VLSB)
 test_constructor(bytearray(8), 8, 1, framebuf.MONO_VLSB)
 test_constructor(bytearray(7), 8, 1, framebuf.MONO_VLSB)
 test_constructor(bytearray(8), 8, 8, framebuf.MONO_VLSB)
+test_constructor(bytearray(1), 1, 8, framebuf.MONO_VLSB)
+test_constructor(bytearray(1), 1, 9, framebuf.MONO_VLSB)
+test_constructor(bytearray(2), 1, 9, framebuf.MONO_VLSB)
+test_constructor(bytearray(1), 1, 8, framebuf.MONO_VLSB, 10)
+test_constructor(bytearray(8), 8, 8, framebuf.MONO_VLSB, 10)
+test_constructor(bytearray(8), 8, 8, framebuf.MONO_VLSB, 7)
+test_constructor(bytearray(11), 1, 9, framebuf.MONO_VLSB, 10)
+test_constructor(bytearray(10), 1, 9, framebuf.MONO_VLSB, 10)
+test_constructor(bytearray(11), 1, 16, framebuf.MONO_VLSB, 10)
 
 for f in (framebuf.MONO_HLSB, framebuf.MONO_HMSB):
     print(f)
@@ -40,21 +54,37 @@ def test_constructor(*args):
 test_constructor(bytearray(15), 5, 8, framebuf.GS2_HMSB)
 test_constructor(bytearray(16), 5, 8, framebuf.GS2_HMSB)
 test_constructor(bytearray(9), 4, 9, framebuf.GS2_HMSB)
+test_constructor(bytearray(2), 7, 1, framebuf.GS2_HMSB, 9)
+test_constructor(bytearray(4), 7, 2, framebuf.GS2_HMSB, 9)
+test_constructor(bytearray(5), 7, 2, framebuf.GS2_HMSB, 9)
 
 print(framebuf.GS4_HMSB)
 test_constructor(bytearray(8), 2, 8, framebuf.GS4_HMSB)
 test_constructor(bytearray(15), 3, 8, framebuf.GS4_HMSB)
 test_constructor(bytearray(16), 3, 8, framebuf.GS4_HMSB)
 test_constructor(bytearray(9), 2, 9, framebuf.GS4_HMSB)
+test_constructor(bytearray(4), 7, 1, framebuf.GS4_HMSB, 9)
+test_constructor(bytearray(8), 7, 2, framebuf.GS4_HMSB, 9)
+test_constructor(bytearray(9), 7, 2, framebuf.GS4_HMSB, 9)
 
 print(framebuf.GS8)
 test_constructor(bytearray(63), 8, 8, framebuf.GS8)
 test_constructor(bytearray(64), 8, 8, framebuf.GS8)
 test_constructor(bytearray(64), 9, 8, framebuf.GS8)
 test_constructor(bytearray(64), 8, 9, framebuf.GS8)
+test_constructor(bytearray(64), 4, 8, framebuf.GS8, 8)
+test_constructor(bytearray(64), 4, 8, framebuf.GS8, 9)
+test_constructor(bytearray(8), 8, 1, framebuf.GS8, 10)
+test_constructor(bytearray(17), 8, 2, framebuf.GS8, 10)
+test_constructor(bytearray(18), 8, 2, framebuf.GS8, 10)
 
 print(framebuf.RGB565)
 test_constructor(bytearray(127), 8, 8, framebuf.RGB565)
 test_constructor(bytearray(128), 8, 8, framebuf.RGB565)
 test_constructor(bytearray(128), 9, 8, framebuf.RGB565)
 test_constructor(bytearray(128), 8, 9, framebuf.RGB565)
+test_constructor(bytearray(128), 4, 8, framebuf.RGB565, 8)
+test_constructor(bytearray(128), 4, 8, framebuf.RGB565, 9)
+test_constructor(bytearray(16), 8, 1, framebuf.RGB565, 10)
+test_constructor(bytearray(34), 8, 2, framebuf.RGB565, 10)
+test_constructor(bytearray(36), 8, 2, framebuf.RGB565, 10)

tests/extmod/framebuf_bounds.py.exp

@@ -6,10 +6,24 @@ Valid
 Valid
 ValueError
 ValueError
+Valid
+ValueError
+Valid
+ValueError
+Valid
 0
 Valid
 ValueError
 Valid
+Valid
+ValueError
+Valid
+Valid
+Valid
+ValueError
+Valid
+ValueError
+Valid
 3
 Valid
 ValueError
@@ -27,18 +41,34 @@ Valid
 ValueError
 Valid
 Valid
+Valid
+ValueError
+Valid
 2
 Valid
 ValueError
 Valid
 Valid
+Valid
+ValueError
+Valid
 6
 ValueError
 Valid
 ValueError
 ValueError
+Valid
+ValueError
+Valid
+ValueError
+Valid
 1
 ValueError
 Valid
 ValueError
 ValueError
+Valid
+ValueError
+Valid
+ValueError
+Valid