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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Kim Phillips <kim.phillips@amd.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Borislav Petkov <bp@suse.de>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.18 146/231] x86/sev: Avoid using __x86_return_thunk
Date:   Tue, 19 Jul 2022 13:53:51 +0200
Message-Id: <20220719114726.628551296@linuxfoundation.org>
In-Reply-To: <20220719114714.247441733@linuxfoundation.org>
References: <20220719114714.247441733@linuxfoundation.org>
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From: Kim Phillips <kim.phillips@amd.com>

[ Upstream commit 0ee9073000e8791f8b134a8ded31bcc767f7f232 ]

Specifically, it's because __enc_copy() encrypts the kernel after
being relocated outside the kernel in sme_encrypt_execute(), and the
RET macro's jmp offset isn't amended prior to execution.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/mm/mem_encrypt_boot.S | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt_boot.S b/arch/x86/mm/mem_encrypt_boot.S
index 3d1dba05fce4..d94dea450fa6 100644
--- a/arch/x86/mm/mem_encrypt_boot.S
+++ b/arch/x86/mm/mem_encrypt_boot.S
@@ -65,7 +65,9 @@ SYM_FUNC_START(sme_encrypt_execute)
 	movq	%rbp, %rsp		/* Restore original stack pointer */
 	pop	%rbp
 
-	RET
+	/* Offset to __x86_return_thunk would be wrong here */
+	ret
+	int3
 SYM_FUNC_END(sme_encrypt_execute)
 
 SYM_FUNC_START(__enc_copy)
@@ -151,6 +153,8 @@ SYM_FUNC_START(__enc_copy)
 	pop	%r12
 	pop	%r15
 
-	RET
+	/* Offset to __x86_return_thunk would be wrong here */
+	ret
+	int3
 .L__enc_copy_end:
 SYM_FUNC_END(__enc_copy)
-- 
2.35.1