linux-kernel - Re: [PATCH] powerpc: Clean up tm_abort duplication in hash_utils

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <6642c870-763d-c896-aab4-a1bc36bb9015@linux.vnet.ibm.com>
Date:   Fri, 2 Sep 2016 10:52:38 +0800
From:   Rui Teng <rui.teng@...ux.vnet.ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, paulus@...ba.org
Subject: Re: [PATCH] powerpc: Clean up tm_abort duplication in hash_utils_64.c

On 9/1/16 11:46 PM, Thiago Jung Bauermann wrote:
> Am Freitag, 26 August 2016, 11:50:10 schrieb Rui Teng:
>> The same logic appears twice and should probably be pulled out into a
>> function.
>>
>> Suggested-by: Michael Ellerman <mpe@...erman.id.au>
>> Signed-off-by: Rui Teng <rui.teng@...ux.vnet.ibm.com>
>> ---
>>  arch/powerpc/mm/hash_utils_64.c | 45
>> +++++++++++++++++------------------------ 1 file changed, 19
>> insertions(+), 26 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/hash_utils_64.c
>> b/arch/powerpc/mm/hash_utils_64.c index 0821556..69ef702 100644
>> --- a/arch/powerpc/mm/hash_utils_64.c
>> +++ b/arch/powerpc/mm/hash_utils_64.c
>> @@ -1460,6 +1460,23 @@ out_exit:
>>  	local_irq_restore(flags);
>>  }
>>
>> +/*
>> + * Transactions are not aborted by tlbiel, only tlbie.
>> + * Without, syncing a page back to a block device w/ PIO could pick up
>> + * transactional data (bad!) so we force an abort here.  Before the
>> + * sync the page will be made read-only, which will flush_hash_page.
>> + * BIG ISSUE here: if the kernel uses a page from userspace without
>> + * unmapping it first, it may see the speculated version.
>> + */
>> +void local_tm_abort(int local)
>> +{
>> +	if (local && cpu_has_feature(CPU_FTR_TM) && current->thread.regs &&
>> +		MSR_TM_ACTIVE(current->thread.regs->msr)) {
>> +		tm_enable();
>> +		tm_abort(TM_CAUSE_TLBI);
>> +	}
>> +}
>> +
>
> Since local_tm_abort is only used in this file, it should be static.
OK
>
> Also, since both places calling it are guarded by
> CONFIG_PPC_TRANSACTIONAL_MEM, wouldn't it be cleaner if the #ifdef was here
> instead and the #else block defined an empty static inline function? Then
> the call sites wouldn't need to be guarded.
I have considered this style before, but I am worried about the call
stacks increased by empty function and forgot the inline function.
Will send v2 with your comments.

Thanks!

>