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From: Roman Gushchin <klamm@yandex-team.ru>
To: Andrew Shewmaker <agshew@gmail.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] mm: fix arithmetic overflow in __vm_enough_memory()
Date: Fri, 30 Jan 2015 16:14:10 +0300	[thread overview]
Message-ID: <66011422623650@webcorp02h.yandex-team.ru> (raw)
In-Reply-To: <20150129195735.GA9331@scruffy>

29.01.2015, 22:57, "Andrew Shewmaker" <agshew@gmail.com>:
> On Thu, Jan 29, 2015 at 04:06:03PM +0300, Roman Gushchin wrote:
>>  I noticed, that "allowed" can easily overflow by falling below 0,
>>  because (total_vm / 32) can be larger than "allowed". The problem
>>  occurs in OVERCOMMIT_NONE mode.
>>

> Makes sense to me. Please fix mm/nommu.c also.

Thanks!
I sent a patch for nommu.c.

>
> If a caller passes in a big negative value for pages,
> then vm_acct_memory() would decrement vm_committed_as, possibly
> causing percpu_counter_read_positive(&vm_committed_as) and
> __vm_enough_memory to return 0. Maybe that's okay? Callers
> won't be passing in a negative pages anyway. Is there a reason
> to let them, though?

I think, it isn't a problem, since no one will commit negative values (I hope).

R.

WARNING: multiple messages have this Message-ID (diff)
From: Roman Gushchin <klamm@yandex-team.ru>
To: Andrew Shewmaker <agshew@gmail.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] mm: fix arithmetic overflow in __vm_enough_memory()
Date: Fri, 30 Jan 2015 16:14:10 +0300	[thread overview]
Message-ID: <66011422623650@webcorp02h.yandex-team.ru> (raw)
In-Reply-To: <20150129195735.GA9331@scruffy>

29.01.2015, 22:57, "Andrew Shewmaker" <agshew@gmail.com>:
> On Thu, Jan 29, 2015 at 04:06:03PM +0300, Roman Gushchin wrote:
>> О©╫I noticed, that "allowed" can easily overflow by falling below 0,
>> О©╫because (total_vm / 32) can be larger than "allowed". The problem
>> О©╫occurs in OVERCOMMIT_NONE mode.
>>

> Makes sense to me. Please fix mm/nommu.c also.

Thanks!
I sent a patch for nommu.c.

>
> If a caller passes in a big negative value for pages,
> then vm_acct_memory() would decrement vm_committed_as, possibly
> causing percpu_counter_read_positive(&vm_committed_as) and
> __vm_enough_memory to return 0. Maybe that's okay? Callers
> won't be passing in a negative pages anyway. Is there a reason
> to let them, though?

I think, it isn't a problem, since no one will commit negative values (I hope).

R.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

WARNING: multiple messages have this Message-ID (diff)
From: Roman Gushchin <klamm@yandex-team.ru>
To: Andrew Shewmaker <agshew@gmail.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] mm: fix arithmetic overflow in __vm_enough_memory()
Date: Fri, 30 Jan 2015 16:14:10 +0300	[thread overview]
Message-ID: <66011422623650@webcorp02h.yandex-team.ru> (raw)
In-Reply-To: <20150129195735.GA9331@scruffy>

29.01.2015, 22:57, "Andrew Shewmaker" <agshew@gmail.com>:
> On Thu, Jan 29, 2015 at 04:06:03PM +0300, Roman Gushchin wrote:
>> ?I noticed, that "allowed" can easily overflow by falling below 0,
>> ?because (total_vm / 32) can be larger than "allowed". The problem
>> ?occurs in OVERCOMMIT_NONE mode.
>>

> Makes sense to me. Please fix mm/nommu.c also.

Thanks!
I sent a patch for nommu.c.

>
> If a caller passes in a big negative value for pages,
> then vm_acct_memory() would decrement vm_committed_as, possibly
> causing percpu_counter_read_positive(&vm_committed_as) and
> __vm_enough_memory to return 0. Maybe that's okay? Callers
> won't be passing in a negative pages anyway. Is there a reason
> to let them, though?

I think, it isn't a problem, since no one will commit negative values (I hope).

R.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  parent reply	other threads:[~2015-01-30 13:14 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-29 13:06 [PATCH] mm: fix arithmetic overflow in __vm_enough_memory() Roman Gushchin
2015-01-29 13:06 ` Roman Gushchin
2015-01-29 19:57 ` Andrew Shewmaker
2015-01-29 19:57   ` Andrew Shewmaker
2015-01-30 13:09   ` [PATCH] mm/nommu.c: " Roman Gushchin
2015-01-30 13:14   ` Roman Gushchin [this message]
2015-01-30 13:14     ` [PATCH] mm: " Roman Gushchin
2015-01-30 13:14     ` Roman Gushchin
2015-02-03 13:29 ` Michal Hocko
2015-02-03 13:29   ` Michal Hocko

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