From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Michael Wang <yun.wang@linux.alibaba.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 063/207] x86: Increase exception stack sizes
Date:   Wed, 24 Nov 2021 12:55:34 +0100
Message-Id: <20211124115705.965579826@linuxfoundation.org>
In-Reply-To: <20211124115703.941380739@linuxfoundation.org>
References: <20211124115703.941380739@linuxfoundation.org>
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From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 7fae4c24a2b84a66c7be399727aca11e7a888462 ]

It turns out that a single page of stack is trivial to overflow with
all the tracing gunk enabled. Raise the exception stacks to 2 pages,
which is still half the interrupt stacks, which are at 4 pages.

Reported-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YUIO9Ye98S5Eb68w@hirez.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/include/asm/page_64_types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 390fdd39e0e21..5a69eee673536 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -19,7 +19,7 @@
 #define THREAD_SIZE  (PAGE_SIZE << THREAD_SIZE_ORDER)
 #define CURRENT_MASK (~(THREAD_SIZE - 1))
 
-#define EXCEPTION_STACK_ORDER (0 + KASAN_STACK_ORDER)
+#define EXCEPTION_STACK_ORDER (1 + KASAN_STACK_ORDER)
 #define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
 
 #define DEBUG_STACK_ORDER (EXCEPTION_STACK_ORDER + 1)
-- 
2.33.0