Messages in this thread | | | Date | Mon, 22 Oct 2012 20:43:50 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] blkcg: Fix use-after-free of q->root_blkg and q->root_rl.blkg |
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On 2012-10-17 10:45, Jun'ichi Nomura wrote: > 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.
Thanks, applied to for-linus (and marked stable).
-- Jens Axboe
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