From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1g9XQW-0002IM-CV for kexec@lists.infradead.org; Mon, 08 Oct 2018 15:26:34 +0000 From: Sasha Levin Subject: [PATCH AUTOSEL 4.18 58/58] x86/boot: Fix kexec booting failure in the SEV bit detection code Date: Mon, 8 Oct 2018 11:25:23 -0400 Message-Id: <20181008152523.70705-58-sashal@kernel.org> In-Reply-To: <20181008152523.70705-1-sashal@kernel.org> References: <20181008152523.70705-1-sashal@kernel.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: ghook@redhat.com, brijesh.singh@amd.com, Kairui Song , bhe@redhat.com, kexec@lists.infradead.org, Sasha Levin , mingo@redhat.com, hpa@zytor.com, tglx@linutronix.de, Borislav Petkov , dyoung@redhat.com From: Kairui Song [ Upstream commit bdec8d7fa55e6f5314ed72e5a0b435d90ff90548 ] Commit 1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active") can occasionally cause system resets when kexec-ing a second kernel even if SEV is not active. That's because get_sev_encryption_bit() uses 32-bit rIP-relative addressing to read the value of enc_bit - a variable which caches a previously detected encryption bit position - but kexec may allocate the early boot code to a higher location, beyond the 32-bit addressing limit. In this case, garbage will be read and get_sev_encryption_bit() will return the wrong value, leading to accessing memory with the wrong encryption setting. Therefore, remove enc_bit, and thus get rid of the need to do 32-bit rIP-relative addressing in the first place. [ bp: massage commit message heavily. ] Fixes: 1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active") Suggested-by: Borislav Petkov Signed-off-by: Kairui Song Signed-off-by: Borislav Petkov Reviewed-by: Tom Lendacky Cc: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de Cc: mingo@redhat.com Cc: hpa@zytor.com Cc: brijesh.singh@amd.com Cc: kexec@lists.infradead.org Cc: dyoung@redhat.com Cc: bhe@redhat.com Cc: ghook@redhat.com Link: https://lkml.kernel.org/r/20180927123845.32052-1-kasong@redhat.com Signed-off-by: Sasha Levin --- arch/x86/boot/compressed/mem_encrypt.S | 19 ------------------- 1 file changed, 19 deletions(-) diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S index eaa843a52907..a480356e0ed8 100644 --- a/arch/x86/boot/compressed/mem_encrypt.S +++ b/arch/x86/boot/compressed/mem_encrypt.S @@ -25,20 +25,6 @@ ENTRY(get_sev_encryption_bit) push %ebx push %ecx push %edx - push %edi - - /* - * RIP-relative addressing is needed to access the encryption bit - * variable. Since we are running in 32-bit mode we need this call/pop - * sequence to get the proper relative addressing. - */ - call 1f -1: popl %edi - subl $1b, %edi - - movl enc_bit(%edi), %eax - cmpl $0, %eax - jge .Lsev_exit /* Check if running under a hypervisor */ movl $1, %eax @@ -69,15 +55,12 @@ ENTRY(get_sev_encryption_bit) movl %ebx, %eax andl $0x3f, %eax /* Return the encryption bit location */ - movl %eax, enc_bit(%edi) jmp .Lsev_exit .Lno_sev: xor %eax, %eax - movl %eax, enc_bit(%edi) .Lsev_exit: - pop %edi pop %edx pop %ecx pop %ebx @@ -113,8 +96,6 @@ ENTRY(set_sev_encryption_mask) ENDPROC(set_sev_encryption_mask) .data -enc_bit: - .int 0xffffffff #ifdef CONFIG_AMD_MEM_ENCRYPT .balign 8 -- 2.17.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec