1From d48ec5e1a5fb7907520dee71b1d94045486a0c29 Mon Sep 17 00:00:00 2001
2From: Alexander Kamensky <alexander.kamensky42@gmail.com>
3Date: Thu, 12 Nov 2020 12:56:46 -0800
4Subject: [PATCH] arm64: kexec: disabled check if kaslr-seed dtb property was
5 wiped
6
7Kexec when loading arm64 kernel checks if chosen/kaslr-seed dtb property is
8wiped. It's a good assertion to verify proper behavior of kernel. However,
9if bootloader creates and fills kaslr-seed property and kernel is not
10configured with CONFIG_RANDOMIZE_BASE then logic of reading and wiping
11kaslr-seed does not run. As a result kaslr-seed property is not zero and when
12kexec tries to load secondary kernel it fails with the following message:
13
14setup_2nd_dtb: kaslr-seed is not wiped to 0.
15kexec: setup_2nd_dtb failed.
16kexec: load failed.
17
18This was observed on Yocto Project on qemuarm64 machine with 5.8 kernel,
19qemu 5.1.0. Qemu created kaslr-seed property but kernel was not configured
20with CONFIG_RANDOMIZE_BASE.
21
22Although check has some value, there is a use-case where it breaks kexec,
23this patch removes it.
24
25Note in described use-case the fact that kaslr-seed is not wiped and user
26readable through /sys/firmware/fdt or
27/sys/firmware/devicetree/base/chosen/kaslr-seed is not a security problem
28as kaslr is disabled anyway.
29
30Signed-off-by: Alexander Kamensky <alexander.kamensky42@gmail.com>
31Upstream-Status: Submitted [http://lists.infradead.org/pipermail/kexec/2020-November/021740.html]
32---
33 kexec/arch/arm64/kexec-arm64.c | 14 +-------------
34 1 file changed, 1 insertion(+), 13 deletions(-)
35
36Index: kexec-tools-2.0.20/kexec/arch/arm64/kexec-arm64.c
37===================================================================
38--- kexec-tools-2.0.20.orig/kexec/arch/arm64/kexec-arm64.c
39+++ kexec-tools-2.0.20/kexec/arch/arm64/kexec-arm64.c
40@@ -428,7 +428,7 @@ static int setup_2nd_dtb(struct dtb *dtb
41 	int len, range_len;
42 	int nodeoffset;
43 	int new_size;
44-	int result, kaslr_seed;
45+	int result;
46
47 	result = fdt_check_header(dtb->buf);
48
49@@ -499,18 +499,6 @@ static int setup_2nd_dtb(struct dtb *dtb
50 			return result;
51 		}
52 	} else {
53-		kaslr_seed = fdt64_to_cpu(*prop);
54-
55-		/* kaslr_seed must be wiped clean by primary
56-		 * kernel during boot
57-		 */
58-		if (kaslr_seed != 0) {
59-			dbgprintf("%s: kaslr-seed is not wiped to 0.\n",
60-					__func__);
61-			result = -EINVAL;
62-			goto on_error;
63-		}
64-
65 		/*
66 		 * Invoke the getrandom system call with
67 		 * GRND_NONBLOCK, to make sure we
68