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From:   Lai Jiangshan <jiangshanlai@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     x86@kernel.org, Lai Jiangshan <laijs@linux.alibaba.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        "Chang S . Bae" <chang.seok.bae@intel.com>,
        Sasha Levin <sashal@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>
Subject: [PATCH V4 01/50] x86/entry: Add fence for kernel entry swapgs in paranoid_entry()
Date:   Tue, 26 Oct 2021 22:13:31 +0800
Message-Id: <20211026141420.17138-2-jiangshanlai@gmail.com>
In-Reply-To: <20211026141420.17138-1-jiangshanlai@gmail.com>
References: <20211026141420.17138-1-jiangshanlai@gmail.com>
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From: Lai Jiangshan <laijs@linux.alibaba.com>

Commit 18ec54fdd6d18 ("x86/speculation: Prepare entry code for Spectre
v1 swapgs mitigations") adds FENCE_SWAPGS_{KERNEL|USER}_ENTRY
for conditional swapgs.  And in paranoid_entry(), it uses only
FENCE_SWAPGS_KERNEL_ENTRY for both branches.  It is because the fence
is required for both cases since the CR3 write is conditinal even PTI
is enabled.

But commit 96b2371413e8f ("x86/entry/64: Switch CR3 before SWAPGS in
paranoid entry") switches the code order and changes the branches.
And it misses the needed FENCE_SWAPGS_KERNEL_ENTRY for user gsbase case.

Add it back.

Fixes: Commit 96b2371413e8f ("x86/entry/64: Switch CR3 before SWAPGS in paranoid entry")
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Chang S. Bae <chang.seok.bae@intel.com>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
 arch/x86/entry/entry_64.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index e38a4cf795d9..1f98188e83ef 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -898,6 +898,7 @@ SYM_CODE_START_LOCAL(paranoid_entry)
 	rdmsr
 	testl	%edx, %edx
 	jns	.Lparanoid_entry_swapgs
+	FENCE_SWAPGS_KERNEL_ENTRY
 	ret
 
 .Lparanoid_entry_swapgs:
-- 
2.19.1.6.gb485710b