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authorJun'ichi Nomura <j-nomura@ce.jp.nec.com>2012-10-17 17:45:36 +0900
committerJens Axboe <axboe@kernel.dk>2012-10-22 22:00:26 +0200
commit65635cbc37e011e71b208257a25e7c1078cd039b (patch)
tree47e17aaa3008518373d67feed3673942d5decfe5 /block
parent0390c8835690506802fd5d54ea5444f0b9b1708b (diff)
downloadlinux-linaro-stable-65635cbc37e011e71b208257a25e7c1078cd039b.tar.gz
blkcg: Fix use-after-free of q->root_blkg and q->root_rl.blkg
blk_put_rl() does not call blkg_put() for q->root_rl because we don't take request list reference on q->root_blkg. However, if root_blkg is once attached then detached (freed), blk_put_rl() is confused by the bogus pointer in q->root_blkg. For example, with !CONFIG_BLK_DEV_THROTTLING && CONFIG_CFQ_GROUP_IOSCHED, switching IO scheduler from cfq to deadline will cause system stall after the following warning with 3.6: > WARNING: at /work/build/linux/block/blk-cgroup.h:250 > blk_put_rl+0x4d/0x95() > Modules linked in: bridge stp llc sunrpc acpi_cpufreq freq_table mperf > ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 > Pid: 0, comm: swapper/0 Not tainted 3.6.0 #1 > Call Trace: > <IRQ> [<ffffffff810453bd>] warn_slowpath_common+0x85/0x9d > [<ffffffff810453ef>] warn_slowpath_null+0x1a/0x1c > [<ffffffff811d5f8d>] blk_put_rl+0x4d/0x95 > [<ffffffff811d614a>] __blk_put_request+0xc3/0xcb > [<ffffffff811d71a3>] blk_finish_request+0x232/0x23f > [<ffffffff811d76c3>] ? blk_end_bidi_request+0x34/0x5d > [<ffffffff811d76d1>] blk_end_bidi_request+0x42/0x5d > [<ffffffff811d7728>] blk_end_request+0x10/0x12 > [<ffffffff812cdf16>] scsi_io_completion+0x207/0x4d5 > [<ffffffff812c6fcf>] scsi_finish_command+0xfa/0x103 > [<ffffffff812ce2f8>] scsi_softirq_done+0xff/0x108 > [<ffffffff811dcea5>] blk_done_softirq+0x8d/0xa1 > [<ffffffff810915d5>] ? > generic_smp_call_function_single_interrupt+0x9f/0xd7 > [<ffffffff8104cf5b>] __do_softirq+0x102/0x213 > [<ffffffff8108a5ec>] ? lock_release_holdtime+0xb6/0xbb > [<ffffffff8104d2b4>] ? raise_softirq_irqoff+0x9/0x3d > [<ffffffff81424dfc>] call_softirq+0x1c/0x30 > [<ffffffff81011beb>] do_softirq+0x4b/0xa3 > [<ffffffff8104cdb0>] irq_exit+0x53/0xd5 > [<ffffffff8102d865>] smp_call_function_single_interrupt+0x34/0x36 > [<ffffffff8142486f>] call_function_single_interrupt+0x6f/0x80 > <EOI> [<ffffffff8101800b>] ? mwait_idle+0x94/0xcd > [<ffffffff81018002>] ? mwait_idle+0x8b/0xcd > [<ffffffff81017811>] cpu_idle+0xbb/0x114 > [<ffffffff81401fbd>] rest_init+0xc1/0xc8 > [<ffffffff81401efc>] ? csum_partial_copy_generic+0x16c/0x16c > [<ffffffff81cdbd3d>] start_kernel+0x3d4/0x3e1 > [<ffffffff81cdb79e>] ? kernel_init+0x1f7/0x1f7 > [<ffffffff81cdb2dd>] x86_64_start_reservations+0xb8/0xbd > [<ffffffff81cdb3e3>] x86_64_start_kernel+0x101/0x110 This patch clears q->root_blkg and q->root_rl.blkg when root blkg is destroyed. Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: stable@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-cgroup.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index cafcd7431189..3ad5e3fbf579 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -285,6 +285,13 @@ static void blkg_destroy_all(struct request_queue *q)
blkg_destroy(blkg);
spin_unlock(&blkcg->lock);
}
+
+ /*
+ * root blkg is destroyed. Just clear the pointer since
+ * root_rl does not take reference on root blkg.
+ */
+ q->root_blkg = NULL;
+ q->root_rl.blkg = NULL;
}
static void blkg_rcu_free(struct rcu_head *rcu_head)