diff options
| author | Sahitya Tummala <stummala@codeaurora.org> | 2020-03-11 16:07:50 +0530 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-03-12 07:07:38 -0600 |
| commit | 30a2da7b7e225ef6c87a660419ea04d3cef3f6a7 (patch) | |
| tree | aca89c1669572e6dac8df99cf9f2212e420c1420 /block/blk-ioc.c | |
| parent | 596444e7570587867924c3ab025183b1a8726897 (diff) | |
block: Fix use-after-free issue accessing struct io_cq
There is a potential race between ioc_release_fn() and
ioc_clear_queue() as shown below, due to which below kernel
crash is observed. It also can result into use-after-free
issue.
context#1: context#2:
ioc_release_fn() __ioc_clear_queue() gets the same icq
->spin_lock(&ioc->lock); ->spin_lock(&ioc->lock);
->ioc_destroy_icq(icq);
->list_del_init(&icq->q_node);
->call_rcu(&icq->__rcu_head,
icq_free_icq_rcu);
->spin_unlock(&ioc->lock);
->ioc_destroy_icq(icq);
->hlist_del_init(&icq->ioc_node);
This results into below crash as this memory
is now used by icq->__rcu_head in context#1.
There is a chance that icq could be free'd
as well.
22150.386550: <6> Unable to handle kernel write to read-only memory
at virtual address ffffffaa8d31ca50
...
Call trace:
22150.607350: <2> ioc_destroy_icq+0x44/0x110
22150.611202: <2> ioc_clear_queue+0xac/0x148
22150.615056: <2> blk_cleanup_queue+0x11c/0x1a0
22150.619174: <2> __scsi_remove_device+0xdc/0x128
22150.623465: <2> scsi_forget_host+0x2c/0x78
22150.627315: <2> scsi_remove_host+0x7c/0x2a0
22150.631257: <2> usb_stor_disconnect+0x74/0xc8
22150.635371: <2> usb_unbind_interface+0xc8/0x278
22150.639665: <2> device_release_driver_internal+0x198/0x250
22150.644897: <2> device_release_driver+0x24/0x30
22150.649176: <2> bus_remove_device+0xec/0x140
22150.653204: <2> device_del+0x270/0x460
22150.656712: <2> usb_disable_device+0x120/0x390
22150.660918: <2> usb_disconnect+0xf4/0x2e0
22150.664684: <2> hub_event+0xd70/0x17e8
22150.668197: <2> process_one_work+0x210/0x480
22150.672222: <2> worker_thread+0x32c/0x4c8
Fix this by adding a new ICQ_DESTROYED flag in ioc_destroy_icq() to
indicate this icq is once marked as destroyed. Also, ensure
__ioc_clear_queue() is accessing icq within rcu_read_lock/unlock so
that icq doesn't get free'd up while it is still using it.
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Co-developed-by: Pradeep P V K <ppvk@codeaurora.org>
Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-ioc.c')
| -rw-r--r-- | block/blk-ioc.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c index 5ed59ac6ae58..9df50fb507ca 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -84,6 +84,7 @@ static void ioc_destroy_icq(struct io_cq *icq) * making it impossible to determine icq_cache. Record it in @icq. */ icq->__rcu_icq_cache = et->icq_cache; + icq->flags |= ICQ_DESTROYED; call_rcu(&icq->__rcu_head, icq_free_icq_rcu); } @@ -212,15 +213,21 @@ static void __ioc_clear_queue(struct list_head *icq_list) { unsigned long flags; + rcu_read_lock(); while (!list_empty(icq_list)) { struct io_cq *icq = list_entry(icq_list->next, struct io_cq, q_node); struct io_context *ioc = icq->ioc; spin_lock_irqsave(&ioc->lock, flags); + if (icq->flags & ICQ_DESTROYED) { + spin_unlock_irqrestore(&ioc->lock, flags); + continue; + } ioc_destroy_icq(icq); spin_unlock_irqrestore(&ioc->lock, flags); } + rcu_read_unlock(); } /** |