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smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A3989497; Mon, 1 Dec 2025 01:54:27 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 612AB3F73B; Mon, 1 Dec 2025 01:54:33 -0800 (PST) Date: Mon, 1 Dec 2025 09:54:25 +0000 From: Mark Rutland To: Baoquan He , Yeoreum Yun Cc: Breno Leitao , Andrew Morton , pjw@kernel.org, catalin.marinas@arm.com, will@kernel.org, coxu@redhat.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: kernel: initialize missing kexec_buf->random field Message-ID: References: <20251127182644.1577592-1-yeoreum.yun@arm.com> <20251127113706.d89a84f277dab3ad273dde75@linux-foundation.org> <5wel6vqjwwf25hryvg6s7z6aaog7xc3zxjevupt3jn4gntme6d@74wwwmhvvelt> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Dec 01, 2025 at 10:50:47AM +0800, Baoquan He wrote: > On 11/28/25 at 02:01pm, Mark Rutland wrote: > > On Fri, Nov 28, 2025 at 05:55:05AM -0800, Breno Leitao wrote: > > > > > > On Fri, Nov 28, 2025 at 08:17:21AM +0800, Baoquan He wrote: > > > > On 11/27/25 at 11:37am, Andrew Morton wrote: > > > > > On Thu, 27 Nov 2025 18:26:44 +0000 Yeoreum Yun 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. > > > > > > > > This has been fixed in below series from Breno Leitao. > > > > > > > > [PATCH 0/3] kexec: Fix invalid field access > > > > https://lore.kernel.org/all/20250827-kbuf_all-v1-0-1df9882bb01a@debian.org/T/#u > > > > > > Right, these fixes are on 6.18 since day one. > > > > > > Yeoreum is hitting another code path that I haven't fixed, it seems > > > (through image_load()). > > > > > > That said, I think the fix should be similar to commit 04d3cd43700 ("arm64: > > > kexec: initialize kexec_buf struct in load_other_segments()"). I.e: > > > > > > --- a/arch/arm64/kernel/kexec_image.c > > > +++ b/arch/arm64/kernel/kexec_image.c > > > @@ -41,7 +41,7 @@ static void *image_load(struct kimage *image, > > > struct arm64_image_header *h; > > > u64 flags, value; > > > bool be_image, be_kernel; > > > - struct kexec_buf kbuf; > > > + struct kexec_buf kbuf = {}; > > > unsigned long text_offset, kernel_segment_number; > > > struct kexec_segment *kernel_segment; > > > int ret; > > > > FWIW, I completey agree; your proposal is a much better solution. > > Yes, maybe Yeoreum or Breno can post a new version to fix it on arm64. Yep; I hope that Yeoreum will spin a v2 to that effect. > > From a quick scan, it looks like loongarch also has some more dodgy > > instances: > > In the latest mainline kernel, the problem on loongarch has gone. Ah, yep, all the loongarch instances were fixed in v6.18-rc6 by commit: df16b8956cae9700 ("LoongArch: kexec: Initialize the kexec_buf structure") Mark.