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From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Florian Weimer <fweimer@redhat.com>,
	Andreas Schwab <schwab@suse.de>,
	Andrew Senkevich <andrew.n.senkevich@gmail.com>
Cc: nd@arm.com, "H.J. Lu" <hjl.tools@gmail.com>,
	libc-alpha <libc-alpha@sourceware.org>, Max Horn <max@quendi.de>,
	thomas@grindinggear.com
Subject: Re: [PATCH] Fix i386 memmove issue [BZ #22644]
Date: Mon, 19 Mar 2018 14:25:00 -0000	[thread overview]
Message-ID: <e7d81f18-315c-4434-a734-41029c0d387f@arm.com> (raw)
In-Reply-To: <597954a1-85da-e524-1454-27c46af57413@redhat.com>

On 19/03/18 13:17, Florian Weimer wrote:
> On 03/19/2018 02:11 PM, Andreas Schwab wrote:
>> On Mär 19 2018, Andrew Senkevich<andrew.n.senkevich@gmail.com>  wrote:
>>
>>> +static void
>>> +do_test2 (void)
>>> +{
>>> +  uint32_t num = 0x20000000;
>>> +  uint32_t * large_buf;
>>> +
>>> +  large_buf = mmap ((void*)0x70000000, num, PROT_READ | PROT_WRITE,
>>> +     MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);
>> Since you are using MAP_FIXED this may overwrite an existing mapping.
> 
> Leading to a hard-to-debug crash, maybe sporadically due to ASLR.  Yes, I have this concern as well.
> 
> There was a long, long Linux thread about a non-overriding MAP_FIXED variant, but as far as I can see, this has not been merged.  Maybe it would 
> have helped here.
> 

i thought not using MAP_FIXED is the 'non-overriding MAP_FIXED variant'

if you use an address hint then the kernel will use that unless
it's not available and you can check the result.

  parent reply	other threads:[~2018-03-19 14:25 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-19 10:13 Andrew Senkevich
2018-02-19 10:31 ` Andreas Schwab
2018-03-14 14:43   ` Andrew Senkevich
2018-03-14 14:59     ` H.J. Lu
2018-03-19 12:46       ` Andrew Senkevich
2018-03-19 12:55         ` H.J. Lu
2018-03-19 13:11         ` Andreas Schwab
2018-03-19 13:17           ` Florian Weimer
2018-03-19 14:01             ` Andrew Senkevich
2018-03-19 14:25             ` Szabolcs Nagy [this message]
2018-03-19 15:33               ` Florian Weimer
2018-03-19 17:52                 ` Andrew Senkevich
2018-03-19 17:57                   ` H.J. Lu
2018-03-19 19:30                     ` Andrew Senkevich
2018-03-19 19:38                       ` H.J. Lu
2018-03-19 20:33                         ` Andrew Senkevich
2018-03-19 20:50                           ` H.J. Lu
2018-03-20  8:58                           ` Andreas Schwab
2018-03-23 17:15                             ` Andrew Senkevich

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