linux-kernel - Re: [PATCH v4 3/3] riscv: kdump: Fix crash memory reserve exceed system memory bug

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Message-ID: <f0cc1bc6-8fc0-d4a3-0aca-1f3576fa072d@huawei.com>
Date: Mon, 22 Jul 2024 15:49:47 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Mike Rapoport <rppt@...nel.org>
CC: <linux@...linux.org.uk>, <paul.walmsley@...ive.com>, <palmer@...belt.com>,
	<aou@...s.berkeley.edu>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>, <hpa@...or.com>,
	<arnd@...db.de>, <gregkh@...uxfoundation.org>, <deller@....de>,
	<javierm@...hat.com>, <bhe@...hat.com>, <robh@...nel.org>,
	<alexghiti@...osinc.com>, <bjorn@...osinc.com>, <akpm@...ux-foundation.org>,
	<namcao@...utronix.de>, <dawei.li@...ngroup.cn>, <chenjiahao16@...wei.com>,
	<julian.stecklina@...erus-technology.de>, <rafael.j.wysocki@...el.com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-riscv@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] riscv: kdump: Fix crash memory reserve exceed
 system memory bug



On 2024/7/22 15:23, Mike Rapoport wrote:
> On Mon, Jul 22, 2024 at 03:08:29PM +0800, Jinjie Ruan wrote:
>>
>>
>> On 2024/7/22 14:38, Mike Rapoport wrote:
>>> Hi,
>>>
>>> On Mon, Jul 22, 2024 at 11:57:01AM +0800, Jinjie Ruan wrote:
>>>> Similar with x86_32, on Riscv32 Qemu "virt" machine with 1GB memory, the
>>>> crash kernel "crashkernel=4G" is ok as below:
>>>> 	crashkernel reserved: 0x00000000bf400000 - 0x00000001bf400000 (4096 MB)
>>>>
>>>> The cause is that the crash_size is parsed and printed with "unsigned long
>>>> long" data type which is 8 bytes but allocated used with "phys_addr_t"
>>>> which is 4 bytes in memblock_phys_alloc_range().
>>>>
>>>> Fix it by checking if the crash_size is greater than system RAM size and
>>>> warn out as parse_crashkernel_mem() do it if so.
>>>>
>>>> After this patch, it fails and there is no above confusing reserve
>>>> success info.
>>>>
>>>> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
>>>> ---
>>>>  arch/riscv/mm/init.c | 5 +++++
>>>>  1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>>>> index bfa2dea95354..5d66a4937fcd 100644
>>>> --- a/arch/riscv/mm/init.c
>>>> +++ b/arch/riscv/mm/init.c
>>>> @@ -1381,6 +1381,11 @@ static void __init arch_reserve_crashkernel(void)
>>>>  	if (ret)
>>>>  		return;
>>>>  
>>>> +	if (crash_size >= memblock_phys_mem_size()) {
>>>> +		pr_warn("Crashkernel: invalid size.");
>>>> +		return;
>>>> +	}
>>>> +
>>>
>>> What the point of adding three identical checks right after the call to
>>> parse_crashkernel()?
>>>
>>> This check should be there and parse_crashkernel() should return error in
>>> this case.
>>
>> Hi, Mike
>>
>> How about the folling rough patch?
>>
>> --- a/kernel/crash_reserve.c
>> +++ b/kernel/crash_reserve.c
>> @@ -313,7 +313,7 @@ int __init parse_crashkernel(char *cmdline,
>>         if (high && ret == -ENOENT) {
>>                 ret = __parse_crashkernel(cmdline, 0, crash_size,
>>                                 crash_base, suffix_tbl[SUFFIX_HIGH]);
>> -               if (ret || !*crash_size)
>> +               if (ret || !*crash_size || crash_size >= system_ram)
>>                         return -EINVAL;
>>
>>                 /*
>> @@ -332,7 +332,7 @@ int __init parse_crashkernel(char *cmdline,
>>                 *high = true;
>>         }
>>  #endif
>> -       if (!*crash_size)
>> +       if (!*crash_size || crash_size >= system_ram)
>>                 ret = -EINVAL;
>>
> 
> Why no simply
> 
> diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
> index 5b2722a93a48..64312709877d 100644
> --- a/kernel/crash_reserve.c
> +++ b/kernel/crash_reserve.c
> @@ -336,6 +336,9 @@ int __init parse_crashkernel(char *cmdline,
>  	if (!*crash_size)
>  		ret = -EINVAL;
>  
> +	if (*crash_size >= system_ram)
> +		ret = -EINVAL;
> +
>  	return ret;

This is good, thank you!

>  }
>  
>  
>>>
>>>>  	reserve_crashkernel_generic(cmdline, crash_size, crash_base,
>>>>  				    low_size, high);
>>>>  }
>>>> -- 
>>>> 2.34.1
>>>>
>>>
>