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From d48ec5e1a5fb7907520dee71b1d94045486a0c29 Mon Sep 17 00:00:00 2001
From: Alexander Kamensky <alexander.kamensky42@gmail.com>
Date: Thu, 12 Nov 2020 12:56:46 -0800
Subject: [PATCH] arm64: kexec: disabled check if kaslr-seed dtb property was
wiped
Kexec when loading arm64 kernel checks if chosen/kaslr-seed dtb property is
wiped. It's a good assertion to verify proper behavior of kernel. However,
if bootloader creates and fills kaslr-seed property and kernel is not
configured with CONFIG_RANDOMIZE_BASE then logic of reading and wiping
kaslr-seed does not run. As a result kaslr-seed property is not zero and when
kexec tries to load secondary kernel it fails with the following message:
setup_2nd_dtb: kaslr-seed is not wiped to 0.
kexec: setup_2nd_dtb failed.
kexec: load failed.
This was observed on Yocto Project on qemuarm64 machine with 5.8 kernel,
qemu 5.1.0. Qemu created kaslr-seed property but kernel was not configured
with CONFIG_RANDOMIZE_BASE.
Although check has some value, there is a use-case where it breaks kexec,
this patch removes it.
Note in described use-case the fact that kaslr-seed is not wiped and user
readable through /sys/firmware/fdt or
/sys/firmware/devicetree/base/chosen/kaslr-seed is not a security problem
as kaslr is disabled anyway.
Signed-off-by: Alexander Kamensky <alexander.kamensky42@gmail.com>
Upstream-Status: Submitted [http://lists.infradead.org/pipermail/kexec/2020-November/021740.html]
---
kexec/arch/arm64/kexec-arm64.c | 14 +-------------
1 file changed, 1 insertion(+), 13 deletions(-)
diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
index ec6df4b..10238d9 100644
--- a/kexec/arch/arm64/kexec-arm64.c
+++ b/kexec/arch/arm64/kexec-arm64.c
@@ -503,7 +503,7 @@ static int setup_2nd_dtb(struct dtb *dtb, char *command_line, int on_crash)
int len, range_len;
int nodeoffset;
int new_size;
- int i, result, kaslr_seed;
+ int i, result;
result = fdt_check_header(dtb->buf);
@@ -576,18 +576,6 @@ static int setup_2nd_dtb(struct dtb *dtb, char *command_line, int on_crash)
return result;
}
} else {
- kaslr_seed = fdt64_to_cpu(*prop);
-
- /* kaslr_seed must be wiped clean by primary
- * kernel during boot
- */
- if (kaslr_seed != 0) {
- dbgprintf("%s: kaslr-seed is not wiped to 0.\n",
- __func__);
- result = -EINVAL;
- goto on_error;
- }
-
/*
* Invoke the getrandom system call with
* GRND_NONBLOCK, to make sure we
--
2.25.1
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