linux-kernel - Re: [PATCH] arm64: kernel: initialize missing kexec

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Message-Id: <20251127113706.d89a84f277dab3ad273dde75@linux-foundation.org>
Date: Thu, 27 Nov 2025 11:37:06 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com, will@...nel.org, bhe@...hat.com,
 leitao@...ian.org, coxu@...hat.com, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: kernel: initialize missing kexec_buf->random
 field

On Thu, 27 Nov 2025 18:26:44 +0000 Yeoreum Yun <yeoreum.yun@....com> wrote:

> Commit bf454ec31add ("kexec_file: allow to place kexec_buf randomly")
> introduced the kexec_buf->random field to enable random placement of
> kexec_buf.
> 
> However, this field was never properly initialized for kexec images
> that do not need to be placed randomly, leading to the following UBSAN
> warning:
> 
> [  +0.364528] ------------[ cut here ]------------
> [  +0.000019] UBSAN: invalid-load in ./include/linux/kexec.h:210:12
> [  +0.000131] load of value 2 is not a valid value for type 'bool' (aka '_Bool')
> [  +0.000003] CPU: 4 UID: 0 PID: 927 Comm: kexec Not tainted 6.18.0-rc7+ #3 PREEMPT(full)
> [  +0.000002] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
> [  +0.000000] Call trace:
> [  +0.000001]  show_stack+0x24/0x40 (C)
> [  +0.000006]  __dump_stack+0x28/0x48
> [  +0.000002]  dump_stack_lvl+0x7c/0xb0
> [  +0.000002]  dump_stack+0x18/0x34
> [  +0.000001]  ubsan_epilogue+0x10/0x50
> [  +0.000002]  __ubsan_handle_load_invalid_value+0xc8/0xd0
> [  +0.000003]  locate_mem_hole_callback+0x28c/0x2a0
> [  +0.000003]  kexec_locate_mem_hole+0xf4/0x2f0
> [  +0.000001]  kexec_add_buffer+0xa8/0x178
> [  +0.000002]  image_load+0xf0/0x258
> [  +0.000001]  __arm64_sys_kexec_file_load+0x510/0x718
> [  +0.000002]  invoke_syscall+0x68/0xe8
> [  +0.000001]  el0_svc_common+0xb0/0xf8
> [  +0.000002]  do_el0_svc+0x28/0x48
> [  +0.000001]  el0_svc+0x40/0xe8
> [  +0.000002]  el0t_64_sync_handler+0x84/0x140
> [  +0.000002]  el0t_64_sync+0x1bc/0x1c0
> 
> To address this, initialise kexec_buf->random field properly.
> 
> Fixes: bf454ec31add ("kexec_file: allow to place kexec_buf randomly")

Thanks, I'll add a cc:stable to this.