linux-kernel - Re: [PATCH v2 2/2] powerpc: use probe_user

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Date:   Tue, 8 Jan 2019 10:19:31 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     David Hildenbrand <david@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Mike Rapoport <rppt@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v2 2/2] powerpc: use probe_user_read()



Le 08/01/2019 à 10:04, David Hildenbrand a écrit :
> On 08.01.19 08:37, Christophe Leroy wrote:
>> Instead of opencoding, use probe_user_read() to failessly
>> read a user location.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
>> ---
>>   v2: Using probe_user_read() instead of probe_user_address()
>>
>>   arch/powerpc/kernel/process.c   | 12 +-----------
>>   arch/powerpc/mm/fault.c         |  6 +-----
>>   arch/powerpc/perf/callchain.c   | 20 +++-----------------
>>   arch/powerpc/perf/core-book3s.c |  8 +-------
>>   arch/powerpc/sysdev/fsl_pci.c   | 10 ++++------
>>   5 files changed, 10 insertions(+), 46 deletions(-)
>>

[snip]

>> diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
>> index 918be816b097..c8a1b26489f5 100644
>> --- a/arch/powerpc/sysdev/fsl_pci.c
>> +++ b/arch/powerpc/sysdev/fsl_pci.c
>> @@ -1068,13 +1068,11 @@ int fsl_pci_mcheck_exception(struct pt_regs *regs)
>>   	addr += mfspr(SPRN_MCAR);
>>   
>>   	if (is_in_pci_mem_space(addr)) {
>> -		if (user_mode(regs)) {
>> -			pagefault_disable();
>> -			ret = get_user(inst, (__u32 __user *)regs->nip);
>> -			pagefault_enable();
>> -		} else {
>> +		if (user_mode(regs))
>> +			ret = probe_user_read(&inst, (void __user *)regs->nip,
>> +					      sizeof(inst));
> 
> What about also adding probe_user_address ?

Michael doesn't like it, see https://patchwork.ozlabs.org/patch/1007117/

Christophe

> 
>> +		else
>>   			ret = probe_kernel_address((void *)regs->nip, inst);
>> -		}
>>   
>>   		if (!ret && mcheck_handle_load(regs, inst)) {
>>   			regs->nip += 4;
>>
> 
>