45 lines
1.4 KiB
Diff
45 lines
1.4 KiB
Diff
From: Jens Axboe <jaxboe@fusionio.com>
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Date: Sun, 5 Jun 2011 04:01:13 +0000 (+0200)
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Subject: cfq-iosched: fix locking around ioc->ioc_data assignment
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X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=ab4bd22d3cce6977dc039664cc2d052e3147d662
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cfq-iosched: fix locking around ioc->ioc_data assignment
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Since we are modifying this RCU pointer, we need to hold
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the lock protecting it around it.
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This fixes a potential reuse and double free of a cfq
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io_context structure. The bug has been in CFQ for a long
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time, it hit very few people but those it did hit seemed
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to see it a lot.
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Tracked in RH bugzilla here:
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https://bugzilla.redhat.com/show_bug.cgi?id=577968
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Credit goes to Paul Bolle for figuring out that the issue
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was around the one-hit ioc->ioc_data cache. Thanks to his
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hard work the issue is now fixed.
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Cc: stable@kernel.org
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Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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---
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diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
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index 3c7b537..545b8d4 100644
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--- a/block/cfq-iosched.c
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+++ b/block/cfq-iosched.c
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@@ -2772,8 +2772,11 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
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smp_wmb();
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cic->key = cfqd_dead_key(cfqd);
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- if (ioc->ioc_data == cic)
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+ if (rcu_dereference(ioc->ioc_data) == cic) {
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+ spin_lock(&ioc->lock);
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rcu_assign_pointer(ioc->ioc_data, NULL);
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+ spin_unlock(&ioc->lock);
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+ }
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if (cic->cfqq[BLK_RW_ASYNC]) {
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cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
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