From: "Manfred Spraul" <manfred@colorfullife.com>
To: "\"Ulrich Weigand\"" <Ulrich.Weigand@de.ibm.com>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: Deadlock on the mm->mmap_sem
Date: Mon, 17 Sep 2001 23:50:40 +0200 [thread overview]
Message-ID: <001701c13fc2$cda19a90$010411ac@local> (raw)
> What happens is that proc_pid_read_maps grabs the mmap_sem as a
> reader, and *while it holds the lock*, does a copy_to_user. This can
> of course page-fault, and the handler will also grab the mmap_sem
> (if it is the same task).
Ok, that's a bug.
You must not call copy_to_user with the mmap semaphore acquired - linux
semaphores are not recursive.
> Any ideas how to fix this? Should proc_pid_read_maps just drop the
> lock before copy_to_user?
Yes, and preferable switch to multiline copies - a full page temporary
buffer is allocated, transfering data on a line-by-line base is way too
much overhead (and the current volatile_task is an ugly hack).
--
Manfred
next reply other threads:[~2001-09-17 21:50 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-17 21:50 Manfred Spraul [this message]
2001-09-17 23:39 ` Deadlock on the mm->mmap_sem Linus Torvalds
[not found] ` <200109172339.f8HNd5W13244@penguin.transmeta.com>
2001-09-18 0:01 ` Andrea Arcangeli
2001-09-18 7:31 ` Manfred Spraul
2001-09-18 7:55 ` Andrea Arcangeli
2001-09-18 8:18 ` David Howells
2001-09-18 9:32 ` David Howells
2001-09-18 9:37 ` Manfred Spraul
2001-09-18 9:49 ` Arjan van de Ven
2001-09-18 12:53 ` Manfred Spraul
2001-09-18 14:13 ` David Howells
2001-09-18 14:49 ` Alan Cox
2001-09-18 15:26 ` David Howells
2001-09-18 15:46 ` Alan Cox
2001-09-18 15:11 ` David Howells
2001-09-18 16:49 ` Linus Torvalds
2001-09-19 9:51 ` David Howells
2001-09-19 12:49 ` Andrea Arcangeli
2001-09-19 14:08 ` Manfred Spraul
2001-09-19 14:51 ` David Howells
2001-09-19 15:18 ` Manfred Spraul
2001-09-19 14:53 ` David Howells
2001-09-19 18:03 ` Andrea Arcangeli
2001-09-19 18:16 ` Benjamin LaHaise
2001-09-19 18:27 ` David Howells
2001-09-19 18:48 ` Andrea Arcangeli
2001-09-19 18:45 ` Andrea Arcangeli
2001-09-19 21:14 ` Benjamin LaHaise
2001-09-19 22:07 ` Andrea Arcangeli
2001-09-19 18:19 ` Manfred Spraul
2001-09-20 2:07 ` Andrea Arcangeli
2001-09-20 4:37 ` Andrea Arcangeli
2001-09-20 7:05 ` David Howells
2001-09-20 7:19 ` Andrea Arcangeli
2001-09-20 8:01 ` David Howells
2001-09-20 8:09 ` Andrea Arcangeli
2001-09-19 18:26 ` David Howells
2001-09-19 18:47 ` Andrea Arcangeli
2001-09-19 23:25 ` David Howells
2001-09-19 23:34 ` Andrea Arcangeli
2001-09-19 23:46 ` Andrea Arcangeli
2001-09-19 23:24 ` [PATCH] attempt #2 (Re: Deadlock on the mm->mmap_sem) David Howells
2001-09-19 14:58 ` Deadlock on the mm->mmap_sem David Howells
[not found] <masp0008@stud.uni-sb.de>
2001-09-20 10:57 ` Studierende der Universitaet des Saarlandes
2001-09-20 12:40 ` David Howells
2001-09-20 18:24 ` Andrea Arcangeli
2001-09-20 21:43 ` Manfred Spraul
2001-09-22 21:06 ` Manfred Spraul
-- strict thread matches above, loose matches on Subject: below --
2001-09-18 13:22 Ulrich Weigand
2001-09-17 20:57 Ulrich Weigand
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