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 <[email protected]> --- 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 6f572ed..4b9f2d5 100644 --- a/kexec/arch/arm64/kexec-arm64.c +++ b/kexec/arch/arm64/kexec-arm64.c @@ -493,7 +493,7 @@ static int setup_2nd_dtb(struct dtb *dtb, char *command_line, int on_crash) int len, range_len; int nodeoffset; int new_size; - int result, kaslr_seed; + int result; result = fdt_check_header(dtb->buf); @@ -564,18 +564,6 @@ 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 -- 2.26.2 _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
