linux-kernel - [tip: x86/boot] x86/kexec: Ensure preserve_context flag is set on return to kernel

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] [day] [month] [year] [list]

Message-ID: <173693267387.31546.10614687190445554474.tip-bot2@tip-bot2>
Date: Wed, 15 Jan 2025 09:17:53 -0000
From: "tip-bot2 for David Woodhouse" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: David Woodhouse <dwmw@...zon.co.uk>,
 "Borislav Petkov (AMD)" <bp@...en8.de>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/boot] x86/kexec: Ensure preserve_context flag is set on
 return to kernel

The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     4d5f1da98f5e94ecc39d6e7a990db2efe0ae3810
Gitweb:        https://git.kernel.org/tip/4d5f1da98f5e94ecc39d6e7a990db2efe0ae3810
Author:        David Woodhouse <dwmw@...zon.co.uk>
AuthorDate:    Thu, 09 Jan 2025 14:04:14 
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Tue, 14 Jan 2025 12:52:47 +01:00

x86/kexec: Ensure preserve_context flag is set on return to kernel

The swap_pages() function will only actually *swap*, as its name implies, if
the preserve_context flag in the %r11 register is non-zero. On the way back
from a ::preserve_context kexec, ensure that the %r11 register is non-zero so
that the pages get swapped back.

Fixes: 9e5683e2d0b5 ("x86/kexec: Only swap pages for ::preserve_context mode")
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://lore.kernel.org/r/20250109140757.2841269-3-dwmw2@infradead.org
---
 arch/x86/kernel/relocate_kernel_64.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 9bd601d..6fce4b4 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -220,6 +220,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 	movq	kexec_pa_table_page(%rip), %rax
 	movq	%rax, %cr3
 	lea	PAGE_SIZE(%r8), %rsp
+	movl	$1, %r11d	/* Ensure preserve_context flag is set */
 	call	swap_pages
 	movq	kexec_va_control_page(%rip), %rax
 	addq	$(virtual_mapped - relocate_kernel), %rax