[PATCH] arm64: ptrace: user_regset_copyin_ignore() always returns 0

[Sergey Shtylyov]

On 9/22/22 2:59 PM, Will Deacon wrote:
[...]
>> user_regset_copyin_ignore() always return 0, so checking its result seems
>> pointless -- don't do this...
>>
>> Found by Linux Verification Center (linuxtesting.org) with the SVACE static
>> analysis tool.
>>
>> Signed-off-by: Sergey Shtylyov <s.shtylyov at omp.ru>
>>
>> ---
>> This patch is against the 'for-next/core' branch of the ARM64 repo...
>>
>>  arch/arm64/kernel/ptrace.c |   16 ++++------------
>>  1 file changed, 4 insertions(+), 12 deletions(-)
>>
>> Index: linux/arch/arm64/kernel/ptrace.c
>> ===================================================================
>> --- linux.orig/arch/arm64/kernel/ptrace.c
>> +++ linux/arch/arm64/kernel/ptrace.c
>> @@ -514,9 +514,7 @@ static int hw_break_set(struct task_stru
>>  
>>  	/* Resource info and pad */
>>  	offset = offsetof(struct user_hwdebug_state, dbg_regs);
>> -	ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, 0, offset);
>> -	if (ret)
>> -		return ret;
>> +	user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, 0, offset);
>>  
>>  	/* (address, ctrl) registers */
>>  	limit = regset->n * regset->size;
>> @@ -543,11 +541,8 @@ static int hw_break_set(struct task_stru
>>  			return ret;
>>  		offset += PTRACE_HBP_CTRL_SZ;
>>  
>> -		ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf,
>> -						offset,
>> -						offset + PTRACE_HBP_PAD_SZ);
>> -		if (ret)
>> -			return ret;
>> +		user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf,
>> +					  offset, offset + PTRACE_HBP_PAD_SZ);
>>  		offset += PTRACE_HBP_PAD_SZ;
>>  		idx++;
>>  	}
>> @@ -939,10 +934,7 @@ static int sve_set_common(struct task_st
>>  
>>  	start = end;
>>  	end = SVE_PT_SVE_FPSR_OFFSET(vq);
>> -	ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf,
>> -					start, end);
>> -	if (ret)
>> -		goto out;
>> +	user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, start, end);
> 
> I think it would be better to have user_regset_copyin_ignore() return void
> so that we don't run the risk of missing an error code if it starts
> returning one in future.

   That's the plan! But I need to convert the users 1st, right?

> Will

MBR, Sergey