| Andrew Geissler | 6ce62a2 | 2020-11-30 19:58:47 -0600 | [diff] [blame] | 1 | From d48ec5e1a5fb7907520dee71b1d94045486a0c29 Mon Sep 17 00:00:00 2001 |
| 2 | From: Alexander Kamensky <alexander.kamensky42@gmail.com> |
| 3 | Date: Thu, 12 Nov 2020 12:56:46 -0800 |
| 4 | Subject: [PATCH] arm64: kexec: disabled check if kaslr-seed dtb property was |
| 5 | wiped |
| 6 | |
| 7 | Kexec when loading arm64 kernel checks if chosen/kaslr-seed dtb property is |
| 8 | wiped. It's a good assertion to verify proper behavior of kernel. However, |
| 9 | if bootloader creates and fills kaslr-seed property and kernel is not |
| 10 | configured with CONFIG_RANDOMIZE_BASE then logic of reading and wiping |
| 11 | kaslr-seed does not run. As a result kaslr-seed property is not zero and when |
| 12 | kexec tries to load secondary kernel it fails with the following message: |
| 13 | |
| 14 | setup_2nd_dtb: kaslr-seed is not wiped to 0. |
| 15 | kexec: setup_2nd_dtb failed. |
| 16 | kexec: load failed. |
| 17 | |
| 18 | This was observed on Yocto Project on qemuarm64 machine with 5.8 kernel, |
| 19 | qemu 5.1.0. Qemu created kaslr-seed property but kernel was not configured |
| 20 | with CONFIG_RANDOMIZE_BASE. |
| 21 | |
| 22 | Although check has some value, there is a use-case where it breaks kexec, |
| 23 | this patch removes it. |
| 24 | |
| 25 | Note in described use-case the fact that kaslr-seed is not wiped and user |
| 26 | readable through /sys/firmware/fdt or |
| 27 | /sys/firmware/devicetree/base/chosen/kaslr-seed is not a security problem |
| 28 | as kaslr is disabled anyway. |
| 29 | |
| 30 | Signed-off-by: Alexander Kamensky <alexander.kamensky42@gmail.com> |
| 31 | Upstream-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 | |
| 36 | Index: 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 |