From: Hillf Danton hdanton@sina.com
commit c4068bf898ddaef791049a366828d9b84b467bda upstream.
The smart syzbot has found a reproducer for the following issue:
================================================================== BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:71 [inline] BUG: KASAN: use-after-free in atomic_inc include/asm-generic/atomic-instrumented.h:240 [inline] BUG: KASAN: use-after-free in io_wqe_inc_running fs/io-wq.c:301 [inline] BUG: KASAN: use-after-free in io_wq_worker_running+0xde/0x110 fs/io-wq.c:613 Write of size 4 at addr ffff8882183db08c by task io_wqe_worker-0/7771
CPU: 0 PID: 7771 Comm: io_wqe_worker-0 Not tainted 5.9.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x198/0x1fd lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383 __kasan_report mm/kasan/report.c:513 [inline] kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 check_memory_region_inline mm/kasan/generic.c:186 [inline] check_memory_region+0x13d/0x180 mm/kasan/generic.c:192 instrument_atomic_write include/linux/instrumented.h:71 [inline] atomic_inc include/asm-generic/atomic-instrumented.h:240 [inline] io_wqe_inc_running fs/io-wq.c:301 [inline] io_wq_worker_running+0xde/0x110 fs/io-wq.c:613 schedule_timeout+0x148/0x250 kernel/time/timer.c:1879 io_wqe_worker+0x517/0x10e0 fs/io-wq.c:580 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Allocated by task 7768: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 kasan_set_track mm/kasan/common.c:56 [inline] __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461 kmem_cache_alloc_node_trace+0x17b/0x3f0 mm/slab.c:3594 kmalloc_node include/linux/slab.h:572 [inline] kzalloc_node include/linux/slab.h:677 [inline] io_wq_create+0x57b/0xa10 fs/io-wq.c:1064 io_init_wq_offload fs/io_uring.c:7432 [inline] io_sq_offload_start fs/io_uring.c:7504 [inline] io_uring_create fs/io_uring.c:8625 [inline] io_uring_setup+0x1836/0x28e0 fs/io_uring.c:8694 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 21: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422 __cache_free mm/slab.c:3418 [inline] kfree+0x10e/0x2b0 mm/slab.c:3756 __io_wq_destroy fs/io-wq.c:1138 [inline] io_wq_destroy+0x2af/0x460 fs/io-wq.c:1146 io_finish_async fs/io_uring.c:6836 [inline] io_ring_ctx_free fs/io_uring.c:7870 [inline] io_ring_exit_work+0x1e4/0x6d0 fs/io_uring.c:7954 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
The buggy address belongs to the object at ffff8882183db000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 140 bytes inside of 1024-byte region [ffff8882183db000, ffff8882183db400) The buggy address belongs to the page: page:000000009bada22b refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2183db flags: 0x57ffe0000000200(slab) raw: 057ffe0000000200 ffffea0008604c48 ffffea00086a8648 ffff8880aa040700 raw: 0000000000000000 ffff8882183db000 0000000100000002 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff8882183daf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff8882183db000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8882183db080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff8882183db100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8882183db180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
which is down to the comment below,
/* all workers gone, wq exit can proceed */ if (!nr_workers && refcount_dec_and_test(&wqe->wq->refs)) complete(&wqe->wq->done);
because there might be multiple cases of wqe in a wq and we would wait for every worker in every wqe to go home before releasing wq's resources on destroying.
To that end, rework wq's refcount by making it independent of the tracking of workers because after all they are two different things, and keeping it balanced when workers come and go. Note the manager kthread, like other workers, now holds a grab to wq during its lifetime.
Finally to help destroy wq, check IO_WQ_BIT_EXIT upon creating worker and do nothing for exiting wq.
Cc: stable@vger.kernel.org # v5.5+ Reported-by: syzbot+45fa0a195b941764e0f0@syzkaller.appspotmail.com Reported-by: syzbot+9af99580130003da82b1@syzkaller.appspotmail.com Cc: Pavel Begunkov asml.silence@gmail.com Signed-off-by: Hillf Danton hdanton@sina.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io-wq.c | 116 ++++++++++++++++++++++++++++++------------------------------- 1 file changed, 58 insertions(+), 58 deletions(-)
--- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -202,7 +202,6 @@ static void io_worker_exit(struct io_wor { struct io_wqe *wqe = worker->wqe; struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker); - unsigned nr_workers;
/* * If we're not at zero, someone else is holding a brief reference @@ -230,15 +229,11 @@ static void io_worker_exit(struct io_wor raw_spin_lock_irq(&wqe->lock); } acct->nr_workers--; - nr_workers = wqe->acct[IO_WQ_ACCT_BOUND].nr_workers + - wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers; raw_spin_unlock_irq(&wqe->lock);
- /* all workers gone, wq exit can proceed */ - if (!nr_workers && refcount_dec_and_test(&wqe->wq->refs)) - complete(&wqe->wq->done); - kfree_rcu(worker, rcu); + if (refcount_dec_and_test(&wqe->wq->refs)) + complete(&wqe->wq->done); }
static inline bool io_wqe_run_queue(struct io_wqe *wqe) @@ -641,7 +636,7 @@ void io_wq_worker_sleeping(struct task_s
static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index) { - struct io_wqe_acct *acct =&wqe->acct[index]; + struct io_wqe_acct *acct = &wqe->acct[index]; struct io_worker *worker;
worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, wqe->node); @@ -674,6 +669,7 @@ static bool create_io_worker(struct io_w if (index == IO_WQ_ACCT_UNBOUND) atomic_inc(&wq->user->processes);
+ refcount_inc(&wq->refs); wake_up_process(worker->task); return true; } @@ -689,28 +685,63 @@ static inline bool io_wqe_need_worker(st return acct->nr_workers < acct->max_workers; }
+static bool io_wqe_worker_send_sig(struct io_worker *worker, void *data) +{ + send_sig(SIGINT, worker->task, 1); + return false; +} + +/* + * Iterate the passed in list and call the specific function for each + * worker that isn't exiting + */ +static bool io_wq_for_each_worker(struct io_wqe *wqe, + bool (*func)(struct io_worker *, void *), + void *data) +{ + struct io_worker *worker; + bool ret = false; + + list_for_each_entry_rcu(worker, &wqe->all_list, all_list) { + if (io_worker_get(worker)) { + /* no task if node is/was offline */ + if (worker->task) + ret = func(worker, data); + io_worker_release(worker); + if (ret) + break; + } + } + + return ret; +} + +static bool io_wq_worker_wake(struct io_worker *worker, void *data) +{ + wake_up_process(worker->task); + return false; +} + /* * Manager thread. Tasked with creating new workers, if we need them. */ static int io_wq_manager(void *data) { struct io_wq *wq = data; - int workers_to_create = num_possible_nodes(); int node;
/* create fixed workers */ - refcount_set(&wq->refs, workers_to_create); + refcount_set(&wq->refs, 1); for_each_node(node) { if (!node_online(node)) continue; - if (!create_io_worker(wq, wq->wqes[node], IO_WQ_ACCT_BOUND)) - goto err; - workers_to_create--; + if (create_io_worker(wq, wq->wqes[node], IO_WQ_ACCT_BOUND)) + continue; + set_bit(IO_WQ_BIT_ERROR, &wq->state); + set_bit(IO_WQ_BIT_EXIT, &wq->state); + goto out; }
- while (workers_to_create--) - refcount_dec(&wq->refs); - complete(&wq->done);
while (!kthread_should_stop()) { @@ -742,12 +773,18 @@ static int io_wq_manager(void *data) if (current->task_works) task_work_run();
- return 0; -err: - set_bit(IO_WQ_BIT_ERROR, &wq->state); - set_bit(IO_WQ_BIT_EXIT, &wq->state); - if (refcount_sub_and_test(workers_to_create, &wq->refs)) +out: + if (refcount_dec_and_test(&wq->refs)) { complete(&wq->done); + return 0; + } + /* if ERROR is set and we get here, we have workers to wake */ + if (test_bit(IO_WQ_BIT_ERROR, &wq->state)) { + rcu_read_lock(); + for_each_node(node) + io_wq_for_each_worker(wq->wqes[node], io_wq_worker_wake, NULL); + rcu_read_unlock(); + } return 0; }
@@ -854,37 +891,6 @@ void io_wq_hash_work(struct io_wq_work * work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT)); }
-static bool io_wqe_worker_send_sig(struct io_worker *worker, void *data) -{ - send_sig(SIGINT, worker->task, 1); - return false; -} - -/* - * Iterate the passed in list and call the specific function for each - * worker that isn't exiting - */ -static bool io_wq_for_each_worker(struct io_wqe *wqe, - bool (*func)(struct io_worker *, void *), - void *data) -{ - struct io_worker *worker; - bool ret = false; - - list_for_each_entry_rcu(worker, &wqe->all_list, all_list) { - if (io_worker_get(worker)) { - /* no task if node is/was offline */ - if (worker->task) - ret = func(worker, data); - io_worker_release(worker); - if (ret) - break; - } - } - - return ret; -} - void io_wq_cancel_all(struct io_wq *wq) { int node; @@ -1117,12 +1123,6 @@ bool io_wq_get(struct io_wq *wq, struct return refcount_inc_not_zero(&wq->use_refs); }
-static bool io_wq_worker_wake(struct io_worker *worker, void *data) -{ - wake_up_process(worker->task); - return false; -} - static void __io_wq_destroy(struct io_wq *wq) { int node;