[PATCH AUTOSEL 4.19 26/27] x86/entry: Increase entry_stack size to a full page

[Sasha Levin]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

[ Upstream commit c7aadc09321d8f9a1d3bd1e6d8a47222ecddf6c5 ]

Marco crashed in bad_iret with a Clang11/KCSAN build due to
overflowing the stack. Now that we run C code on it, expand it to a
full page.

Suggested-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Reported-by: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Tested-by: Marco Elver <elver@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200618144801.819246178@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/include/asm/processor.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index efb44bd3a7140..0f750e7b24071 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -336,7 +336,7 @@ struct x86_hw_tss {
 #define INVALID_IO_BITMAP_OFFSET	0x8000
 
 struct entry_stack {
-	unsigned long		words[64];
+	char	stack[PAGE_SIZE];
 };
 
 struct entry_stack_page {
-- 
2.25.1