linux-kernel - [PATCH AUTOSEL 4.4 2/5] x86/kexec: Use up-to-dated screen

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Date:   Mon,  2 Nov 2020 20:21:15 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Kairui Song <kasong@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.4 2/5] x86/kexec: Use up-to-dated screen_info copy to fill boot params

From: Kairui Song <kasong@...hat.com>

[ Upstream commit afc18069a2cb7ead5f86623a5f3d4ad6e21f940d ]

kexec_file_load() currently reuses the old boot_params.screen_info,
but if drivers have change the hardware state, boot_param.screen_info
could contain invalid info.

For example, the video type might be no longer VGA, or the frame buffer
address might be changed. If the kexec kernel keeps using the old screen_info,
kexec'ed kernel may attempt to write to an invalid framebuffer
memory region.

There are two screen_info instances globally available, boot_params.screen_info
and screen_info. Later one is a copy, and is updated by drivers.

So let kexec_file_load use the updated copy.

[ mingo: Tidied up the changelog. ]

Signed-off-by: Kairui Song <kasong@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20201014092429.1415040-2-kasong@redhat.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/kexec-bzimage64.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 0bf17576dd2af..299e7fb55f16e 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -212,8 +212,7 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
 	params->hdr.hardware_subarch = boot_params.hdr.hardware_subarch;

 	/* Copying screen_info will do? */
-	memcpy(&params->screen_info, &boot_params.screen_info,
-				sizeof(struct screen_info));
+	memcpy(&params->screen_info, &screen_info, sizeof(struct screen_info));

 	/* Fill in memsize later */
 	params->screen_info.ext_mem_k = 0;
-- 
2.27.0