From: David Howells <dhowells@redhat.com>
To: Michel Lespinasse <walken@google.com>
Cc: dhowells@redhat.com,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Waychison <mikew@google.com>,
Suleiman Souhlal <suleiman@google.com>,
Ying Han <yinghan@google.com>
Subject: Re: [PATCH 12/12] Use down_read_unfair() for /sys/<pid>/exe and /sys/<pid>/maps files
Date: Wed, 12 May 2010 14:10:38 +0100 [thread overview]
Message-ID: <10175.1273669838@redhat.com> (raw)
In-Reply-To: <1273634462-2672-13-git-send-email-walken@google.com>
Michel Lespinasse <walken@google.com> wrote:
> - Thread C is a monitoring process trying to read every /proc/pid/maps
> in the system. This requires acquiring the mmap_sem for read. Thread C
> blocks behind B, waiting for A to release the rwsem. If thread C
> could be allowed to run in parallel with A, it would probably get done
> long before thread A's disk access completes, thus not actually slowing
> down thread B.
Is it possible for someone to execute a DoS attack on another process using
a bunch of threads reading /proc/pid/maps?
David
next prev parent reply other threads:[~2010-05-12 13:11 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-12 3:20 [PATCH 00/12] rwsem changes + down_read_unfair() proposal Michel Lespinasse
2010-05-12 3:20 ` [PATCH 01/12] rwsem: test for no active locks in __rwsem_do_wake undo code Michel Lespinasse
2010-05-12 10:39 ` David Howells
2010-05-12 3:20 ` [PATCH 02/12] rwsem: use single atomic update for sem count when waking up readers Michel Lespinasse
2010-05-12 11:01 ` David Howells
2010-05-13 0:54 ` Michel Lespinasse
2010-05-12 11:36 ` David Howells
2010-05-12 3:20 ` [PATCH 03/12] rwsem: let RWSEM_WAITING_BIAS represent any number of waiting threads Michel Lespinasse
2010-05-12 3:20 ` [PATCH 04/12] rwsem: consistently use adjustment variable Michel Lespinasse
2010-05-12 11:45 ` David Howells
2010-05-13 1:12 ` Michel Lespinasse
2010-05-12 3:20 ` [PATCH 05/12] x86 rwsem: take advantage of new RWSEM_WAITING_BIAS semantics Michel Lespinasse
2010-05-12 12:10 ` David Howells
2010-05-12 3:20 ` [PATCH 06/12] rwsem: wake queued readers when other readers are active Michel Lespinasse
2010-05-12 12:22 ` David Howells
2010-05-13 2:39 ` Michel Lespinasse
2010-05-13 5:41 ` Michel Lespinasse
2010-05-12 3:20 ` [PATCH 07/12] rwsem: wake queued readers when writer blocks on active read lock Michel Lespinasse
2010-05-12 12:33 ` David Howells
2010-05-12 3:20 ` [PATCH 08/12] rwsem: smaller wrappers around rwsem_down_failed_common Michel Lespinasse
2010-05-12 12:36 ` David Howells
2010-05-12 12:42 ` David Howells
2010-05-13 2:54 ` Michel Lespinasse
2010-05-12 3:20 ` [PATCH 09/12] generic rwsem: implement down_read_unfair Michel Lespinasse
2010-05-12 12:46 ` David Howells
2010-05-12 3:21 ` [PATCH 10/12] rwsem: down_read_unfair infrastructure support Michel Lespinasse
2010-05-12 3:21 ` [PATCH 11/12] x86 rwsem: down_read_unfair implementation Michel Lespinasse
2010-05-12 13:08 ` David Howells
2010-05-12 3:21 ` [PATCH 12/12] Use down_read_unfair() for /sys/<pid>/exe and /sys/<pid>/maps files Michel Lespinasse
2010-05-12 13:10 ` David Howells [this message]
2010-05-12 22:53 ` KOSAKI Motohiro
2010-05-12 23:35 ` Michel Lespinasse
2010-05-13 0:32 ` KOSAKI Motohiro
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