linux-kernel - [PATCH 5.18 19/70] x86/sev: Avoid using __x86_return

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220722090651.799178181@linuxfoundation.org>
Date:   Fri, 22 Jul 2022 11:07:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kim Phillips <kim.phillips@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: [PATCH 5.18 19/70] x86/sev: Avoid using __x86_return_thunk

From: Kim Phillips <kim.phillips@....com>

commit 0ee9073000e8791f8b134a8ded31bcc767f7f232 upstream.

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@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/mm/mem_encrypt_boot.S |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- 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)