From: qiuxishi@huawei•com (Xishi Qiu)
To: linux-arm-kernel@lists•infradead.org
Subject: Have any influence on set_memory_** about below patch ??
Date: Wed, 27 Jan 2016 09:18:57 +0800 [thread overview]
Message-ID: <56A81B01.7010104@huawei.com> (raw)
In-Reply-To: <20160113112813.GE23370@leverpostej>
On 2016/1/13 19:28, Mark Rutland wrote:
> On Wed, Jan 13, 2016 at 01:02:31PM +0800, Xishi Qiu wrote:
>> Hi Mark,
>>
>> If I do like this, does it have the problem too?
>>
>> kmalloc a size
>> no access
>> flush tlb
>> call set_memory_ro to change the page table flag
>> flush tlb
>> start access
>
> This is broken.
>
> The kmalloc will give you memory form the linear mapping. Even if you
> allocate a page, that page could have been mapped with a section at the
> PMD/PUD/PGD level.
>
> Other data could fall within that section (e.g. a kernel stack,
> perhaps).
Hi Mark,
If nobody use that whole section before(however it is almost impossible),
flush tlb is safe, right?
Thanks,
Xishi Qiu
>
> Additional TLB flushees do not help. There's still a race against the
> asynchronous TLB logic. The TLB can allocate or destroy entries at any
> tim. If there were no page table changes prior to the invalidate, the
> TLB could re-allocate all existing entries immediately after the TLB
> invalidate, leaving you in the same state as before.
>
> Thanks,
> Mark.
>
> .
>
next prev parent reply other threads:[~2016-01-27 1:18 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5693A740.7070408@huawei.com>
[not found] ` <20160111133145.GM6499@leverpostej>
2016-01-12 1:20 ` Have any influence on set_memory_** about below patch ?? Xishi Qiu
2016-01-12 11:15 ` Mark Rutland
2016-01-13 4:10 ` Xishi Qiu
2016-01-13 11:22 ` Mark Rutland
2016-01-13 5:02 ` Xishi Qiu
2016-01-13 6:35 ` Xishi Qiu
2016-01-13 11:28 ` Mark Rutland
2016-01-27 1:18 ` Xishi Qiu [this message]
2016-01-27 11:25 ` Mark Rutland
2016-01-26 14:05 ` zhong jiang
2016-01-26 16:07 ` Mark Rutland
2016-01-13 10:30 ` Xishi Qiu
2016-01-13 11:18 ` Mark Rutland
2016-01-14 12:35 ` Xishi Qiu
2016-01-14 13:06 ` Xishi Qiu
2016-01-14 13:44 ` Mark Rutland
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