From: Sahitya Tummala stummala@codeaurora.org
[ Upstream commit 30a2da7b7e225ef6c87a660419ea04d3cef3f6a7 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-ioc.c | 7 +++++++ include/linux/iocontext.h | 1 + 2 files changed, 8 insertions(+)
diff --git a/block/blk-ioc.c b/block/blk-ioc.c index 5ed59ac6ae58b..9df50fb507caf 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(); }
/** diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h index dba15ca8e60bc..1dcd9198beb7f 100644 --- a/include/linux/iocontext.h +++ b/include/linux/iocontext.h @@ -8,6 +8,7 @@
enum { ICQ_EXITED = 1 << 2, + ICQ_DESTROYED = 1 << 3, };
/*