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From: David Miller <davem@davemloft.net>
To: rick.p.edgecombe@intel.com
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
	linux-mm@kvack.org, mroos@linux.ee, mingo@redhat.com,
	namit@vmware.com, luto@kernel.org, bp@alien8.de,
	netdev@vger.kernel.org, dave.hansen@intel.com,
	sparclinux@vger.kernel.org
Subject: Re: [PATCH v2] vmalloc: Fix issues with flush flag
Date: Wed, 22 May 2019 10:40:19 -0700 (PDT)	[thread overview]
Message-ID: <20190522.104019.40493905027242516.davem@davemloft.net> (raw)
In-Reply-To: <339ef85d984f329aa66f29fa80781624e6e4aecc.camel@intel.com>

From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Date: Tue, 21 May 2019 01:59:54 +0000

> On Mon, 2019-05-20 at 18:43 -0700, David Miller wrote:
>> From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
>> Date: Tue, 21 May 2019 01:20:33 +0000
>> 
>> > Should it handle executing an unmapped page gracefully? Because
>> > this
>> > change is causing that to happen much earlier. If something was
>> > relying
>> > on a cached translation to execute something it could find the
>> > mapping
>> > disappear.
>> 
>> Does this work by not mapping any kernel mappings at the beginning,
>> and then filling in the BPF mappings in response to faults?
> No, nothing too fancy. It just flushes the vm mapping immediatly in
> vfree for execute (and RO) mappings. The only thing that happens around
> allocation time is setting of a new flag to tell vmalloc to do the
> flush.
> 
> The problem before was that the pages would be freed before the execute
> mapping was flushed. So then when the pages got recycled, random,
> sometimes coming from userspace, data would be mapped as executable in
> the kernel by the un-flushed tlb entries.

If I am to understand things correctly, there was a case where 'end'
could be smaller than 'start' when doing a range flush.  That would
definitely kill some of the sparc64 TLB flush routines.

  reply	other threads:[~2019-05-22 17:40 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20 20:07 Rick Edgecombe
2019-05-20 21:25 ` Andy Lutomirski
2019-05-20 21:48   ` Edgecombe, Rick P
2019-05-20 21:36 ` Meelis Roos
2019-05-20 22:17   ` Edgecombe, Rick P
2019-05-20 22:48     ` David Miller
2019-05-21  0:20       ` Edgecombe, Rick P
2019-05-21  0:33         ` David Miller
2019-05-21  1:20           ` Edgecombe, Rick P
2019-05-21  1:43             ` David Miller
2019-05-21  1:59               ` Edgecombe, Rick P
2019-05-22 17:40                 ` David Miller [this message]
2019-05-22 19:26                   ` Edgecombe, Rick P
2019-05-22 22:40                     ` Edgecombe, Rick P
2019-05-24 15:50                       ` Edgecombe, Rick P

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