SDL: testautomation_surface: Really make pitch + alignment overflow (62d06)

From 62d063f73572be371bc965633ab054a57fdeda01 Mon Sep 17 00:00:00 2001
From: Simon McVittie <[EMAIL REDACTED]>
Date: Thu, 18 Jan 2024 19:35:33 +0000
Subject: [PATCH] testautomation_surface: Really make pitch + alignment
 overflow

Adding 3 bytes of alignment to 0x7fff'ffff is not enough to make it
overflow a 4-byte unsigned size_t, so this test was not exercising
the intended failure mode. We cannot actually make this overflow
with a signed 32-bit width and an 8-bit format: the maximum width is
not enough to achieve that. However, if we switch to a 24-bit format,
we can make the calculation overflow.

In SDL 2, this test bug was hidden by the fact that allocating
0x7fff'ffff bytes on a 32-bit platform will usually fail, and SDL 2
reported both "malloc() failed" and "this amount of memory is too large
for a size_t" with the same error code.

Signed-off-by: Simon McVittie <smcv@collabora.com>
---
 test/testautomation_surface.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/test/testautomation_surface.c b/test/testautomation_surface.c
index c758bdeeac14..8289e9ccf5e3 100644
--- a/test/testautomation_surface.c
+++ b/test/testautomation_surface.c
@@ -766,7 +766,9 @@ int surface_testOverflow(void *arg)
 
     if (sizeof(size_t) == 4 && sizeof(int) >= 4) {
         expectedError = "Out of memory";
-        surface = SDL_CreateRGBSurfaceWithFormat(0, SDL_MAX_SINT32, 1, 8, SDL_PIXELFORMAT_INDEX8);
+        /* 0x5555'5555 * 3bpp = 0xffff'ffff which fits in size_t, but adding
+         * alignment padding makes it overflow */
+        surface = SDL_CreateRGBSurfaceWithFormat(0, 0x55555555, 1, 24, SDL_PIXELFORMAT_RGB24);
         SDLTest_AssertCheck(surface == NULL, "Should detect overflow in width + alignment");
         SDLTest_AssertCheck(SDL_strcmp(SDL_GetError(), expectedError) == 0,
                             "Expected \"%s\", got \"%s\"", expectedError, SDL_GetError());