Re: [PATCH v16 01/10] riscv: kexec_file: Fix crashk_low_res not exclude bug

[Jinjie Ruan <ruanjinjie@huawei.com>]

On 6/8/2026 3:34 PM, Jinjie Ruan wrote:
> As done in commit 944a45abfabc ("arm64: kdump: Reimplement crashkernel=X")
> and commit 4831be702b95 ("arm64/kexec: Fix missing extra range for
> crashkres_low.") for arm64, while implementing crashkernel=X,[high,low],
> riscv should have excluded the "crashk_low_res" reserved ranges from
> the crash kernel memory to prevent them from being exported through
> /proc/vmcore, and the exclusion would need an extra crash_mem range.
> 
> Just simply tested on qemu with crashkernel=4G with kexec in [1] mentioned
> in [2]. And the second kernel can be started normally.
> 
> 	# dmesg | grep crash
> 	[    0.000000] crashkernel low memory reserved: 0xf8000000 - 0x100000000 (128 MB)
> 	[    0.000000] crashkernel reserved: 0x000000017fe00000 - 0x000000027fe00000 (4096 MB)
> 
> Cc: Guo Ren <guoren@kernel.org>
> Cc: Baoquan He <bhe@redhat.com>
> [1]: https://github.com/chenjh005/kexec-tools/tree/build-test-riscv-v2
> [2]: https://lore.kernel.org/all/20230726175000.2536220-1-chenjiahao16@huawei.com/
> Fixes: 5882e5acf18d ("riscv: kdump: Implement crashkernel=X,[high,low]")
> Reviewed-by: Guo Ren <guoren@kernel.org>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>


The below AI reported TOCTOU bug is an existing artifact and completely
unrelated to this fix here. Therefore, we will skip fixing it in this
series to avoid unnecessary noise.

Link:
https://lore.kernel.org/all/20260608074809.EE4201F00893@smtp.kernel.org/

> ---
>  arch/riscv/kernel/machine_kexec_file.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
> index 54e2d9552e93..3f7766057cac 100644
> --- a/arch/riscv/kernel/machine_kexec_file.c
> +++ b/arch/riscv/kernel/machine_kexec_file.c
> @@ -61,7 +61,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
>  	unsigned int nr_ranges;
>  	int ret;
>  
> -	nr_ranges = 1; /* For exclusion of crashkernel region */
> +	nr_ranges = 2; /* For exclusion of crashkernel region */
>  	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
>  
>  	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
> @@ -76,8 +76,16 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
>  
>  	/* Exclude crashkernel region */
>  	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
> -	if (!ret)
> -		ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
> +	if (ret)
> +		goto out;
> +
> +	if (crashk_low_res.end) {
> +		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
> +		if (ret)
> +			goto out;
> +	}
> +
> +	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
>  
>  out:
>  	kfree(cmem);