[PATCH 0/1] MR7316: win32u: Avoid using uninitialized variable.

[Ruslan Garipov (＠ruslangaripov)]

When dlls/win32u fails to load/initialize the `FreeType font library', a device context object ends up with the only GDI driver attached -- `null_driver`.  The latter implements the `pGetTextMetrics` callback function as do-nothing code.  This causes the `NtGdiGetTextMetricsW()` function to fail not modifying fields of its `metrics` argument.  In result the `normalize_nonclientmetrics()` ends up with uninitialized `tm` local variable after call to the `get_text_metr_size()` function.  Using uninitialized fields of the `TEXTMETRICW` structure gives unpredictable results.

This memset(3)'s the `tm` structure before using.  After that, even if we failed to load the `FreeType font library', the `CaptionHeight', `SmCaptionHeight' and `MenuHeight' metrics keep their current values (the `normalize_nonclientmetrics()` function is called after `get_twips_entry()` callback function, thus value of an entry should not be negative).

[PATCH 1/1] win32u: Avoid using uninitialized variable.

[Ruslan Garipov]

From: Ruslan Garipov

When dlls/win32u fails to load/initialize the `FreeType font library', a
device context object ends up with the only GDI driver attached --
null_driver.  The latter implements the pGetTextMetrics callback
function as do-nothing code.  This causes the NtGdiGetTextMetricsW()
function to fail not modifying fields of its 'metrics' argument.  In
result the normalize_nonclientmetrics() ends up with uninitialized tm
local variable after call to the get_text_metr_size() function.  Using
uninitialized fields of the TEXTMETRICW structure gives unpredictable
results.

This memset(3)'s the tm structure before using.  After that, even if we
failed to load the `FreeType font library', the `CaptionHeight',
`SmCaptionHeight' and `MenuHeight' metrics keep their current values
(the normalize_nonclientmetrics() function is called after
get_twips_entry() callback function, thus value of an entry should not
be negative).

Signed-off-by: Ruslan Garipov 
---
 dlls/win32u/sysparams.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/dlls/win32u/sysparams.c b/dlls/win32u/sysparams.c
index f58bfe14ca2..f911bc542a7 100644
--- a/dlls/win32u/sysparams.c
+++ b/dlls/win32u/sysparams.c
@@ -4910,6 +4910,7 @@ static void normalize_nonclientmetrics( NONCLIENTMETRICSW *pncm)
     if( pncm->iScrollHeight < 8) pncm->iScrollHeight = 8;

/* adjust some heights to the corresponding font */
+    memset( &tm, 0, sizeof tm );
     get_text_metr_size( hdc, &pncm->lfMenuFont, &tm, NULL);
     pncm->iMenuHeight = max( pncm->iMenuHeight, 2 + tm.tmHeight + tm.tmExternalLeading );
     get_text_metr_size( hdc, &pncm->lfCaptionFont, &tm, NULL);