linux-kernel - Re: [PATCH] ARC: entry: fix off-by-one error in syscall number validation

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Date:   Thu, 29 Apr 2021 18:17:20 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Shahab Vahedi <Shahab.Vahedi@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARC: entry: fix off-by-one error in syscall number
 validation

On 4/29/21 4:39 AM, Shahab Vahedi wrote:
> On 4/23/21 9:52 PM, Vineet Gupta wrote:
>> diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
>> index 1743506081da..aea9b558993d 100644
>> --- a/arch/arc/kernel/entry.S
>> +++ b/arch/arc/kernel/entry.S
>> @@ -255,7 +255,7 @@ ENTRY(EV_Trap)
>>   	;============ Normal syscall case
>>   
>>   	; syscall num shd not exceed the total system calls avail
>> -	cmp     r8,  NR_syscalls
>> +	cmp     r8,  NR_syscalls - 1
>>   	mov.hi  r0, -ENOSYS
>>   	bhi     .Lret_from_system_call
> Same problem exists in "syscall Tracing" section:
>
> ; Do the Sys Call as we normally would.
> ; Validate the Sys Call number
> cmp     r8,  NR_syscalls
> mov.hi  r0, -ENOSYS
> bhi     tracesys_exit

Thanks for spotting this. I'll fix this up and repush (after the ongoing 
merge window).

-Vineet