From: Bart Van Assche Date: Sat, 9 Feb 2019 00:59:49 +0000 (-0800) Subject: aio: Fix locking in aio_poll() X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=d3d6a18d7d351cbcc9b33dbedf710e65f8ce1595;p=openwrt%2Fstaging%2Fblogic.git aio: Fix locking in aio_poll() wake_up_locked() may but does not have to be called with interrupts disabled. Since the fuse filesystem calls wake_up_locked() without disabling interrupts aio_poll_wake() may be called with interrupts enabled. Since the kioctx.ctx_lock may be acquired from IRQ context, all code that acquires that lock from thread context must disable interrupts. Hence change the spin_trylock() call in aio_poll_wake() into a spin_trylock_irqsave() call. This patch fixes the following lockdep complaint: ===================================================== WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected 5.0.0-rc4-next-20190131 #23 Not tainted ----------------------------------------------------- syz-executor2/13779 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: 0000000098ac1230 (&fiq->waitq){+.+.}, at: spin_lock include/linux/spinlock.h:329 [inline] 0000000098ac1230 (&fiq->waitq){+.+.}, at: aio_poll fs/aio.c:1772 [inline] 0000000098ac1230 (&fiq->waitq){+.+.}, at: __io_submit_one fs/aio.c:1875 [inline] 0000000098ac1230 (&fiq->waitq){+.+.}, at: io_submit_one+0xedf/0x1cf0 fs/aio.c:1908 and this task is already holding: 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq include/linux/spinlock.h:354 [inline] 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll fs/aio.c:1771 [inline] 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one fs/aio.c:1875 [inline] 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: io_submit_one+0xeb6/0x1cf0 fs/aio.c:1908 which would create a new lock dependency: (&(&ctx->ctx_lock)->rlock){..-.} -> (&fiq->waitq){+.+.} but this new dependency connects a SOFTIRQ-irq-safe lock: (&(&ctx->ctx_lock)->rlock){..-.} ... which became SOFTIRQ-irq-safe at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline] _raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160 spin_lock_irq include/linux/spinlock.h:354 [inline] free_ioctx_users+0x2d/0x4a0 fs/aio.c:610 percpu_ref_put_many include/linux/percpu-refcount.h:285 [inline] percpu_ref_put include/linux/percpu-refcount.h:301 [inline] percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline] percpu_ref_switch_to_atomic_rcu+0x3e7/0x520 lib/percpu-refcount.c:158 __rcu_reclaim kernel/rcu/rcu.h:240 [inline] rcu_do_batch kernel/rcu/tree.c:2486 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2799 [inline] rcu_core+0x928/0x1390 kernel/rcu/tree.c:2780 __do_softirq+0x266/0x95a kernel/softirq.c:292 run_ksoftirqd kernel/softirq.c:654 [inline] run_ksoftirqd+0x8e/0x110 kernel/softirq.c:646 smpboot_thread_fn+0x6ab/0xa10 kernel/smpboot.c:164 kthread+0x357/0x430 kernel/kthread.c:247 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 to a SOFTIRQ-irq-unsafe lock: (&fiq->waitq){+.+.} ... which became SOFTIRQ-irq-unsafe at: ... lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] flush_bg_queue+0x1f3/0x3c0 fs/fuse/dev.c:415 fuse_request_queue_background+0x2d1/0x580 fs/fuse/dev.c:676 fuse_request_send_background+0x58/0x120 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:989 [inline] fuse_fill_super+0x13bb/0x1730 fs/fuse/inode.c:1214 mount_nodev+0x68/0x110 fs/super.c:1392 fuse_mount+0x2d/0x40 fs/fuse/inode.c:1239 legacy_get_tree+0xf2/0x200 fs/fs_context.c:590 vfs_get_tree+0x123/0x450 fs/super.c:1481 do_new_mount fs/namespace.c:2610 [inline] do_mount+0x1436/0x2c40 fs/namespace.c:2932 ksys_mount+0xdb/0x150 fs/namespace.c:3148 __do_sys_mount fs/namespace.c:3162 [inline] __se_sys_mount fs/namespace.c:3159 [inline] __x64_sys_mount+0xbe/0x150 fs/namespace.c:3159 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fiq->waitq); local_irq_disable(); lock(&(&ctx->ctx_lock)->rlock); lock(&fiq->waitq); lock(&(&ctx->ctx_lock)->rlock); *** DEADLOCK *** 1 lock held by syz-executor2/13779: #0: 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq include/linux/spinlock.h:354 [inline] #0: 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll fs/aio.c:1771 [inline] #0: 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one fs/aio.c:1875 [inline] #0: 000000003c46111c (&(&ctx->ctx_lock)->rlock){..-.}, at: io_submit_one+0xeb6/0x1cf0 fs/aio.c:1908 the dependencies between SOFTIRQ-irq-safe lock and the holding lock: -> (&(&ctx->ctx_lock)->rlock){..-.} { IN-SOFTIRQ-W at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline] _raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160 spin_lock_irq include/linux/spinlock.h:354 [inline] free_ioctx_users+0x2d/0x4a0 fs/aio.c:610 percpu_ref_put_many include/linux/percpu-refcount.h:285 [inline] percpu_ref_put include/linux/percpu-refcount.h:301 [inline] percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline] percpu_ref_switch_to_atomic_rcu+0x3e7/0x520 lib/percpu-refcount.c:158 __rcu_reclaim kernel/rcu/rcu.h:240 [inline] rcu_do_batch kernel/rcu/tree.c:2486 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2799 [inline] rcu_core+0x928/0x1390 kernel/rcu/tree.c:2780 __do_softirq+0x266/0x95a kernel/softirq.c:292 run_ksoftirqd kernel/softirq.c:654 [inline] run_ksoftirqd+0x8e/0x110 kernel/softirq.c:646 smpboot_thread_fn+0x6ab/0xa10 kernel/smpboot.c:164 kthread+0x357/0x430 kernel/kthread.c:247 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 INITIAL USE at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline] _raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160 spin_lock_irq include/linux/spinlock.h:354 [inline] __do_sys_io_cancel fs/aio.c:2052 [inline] __se_sys_io_cancel fs/aio.c:2035 [inline] __x64_sys_io_cancel+0xd5/0x5a0 fs/aio.c:2035 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe } ... key at: [] __key.52370+0x0/0x40 ... acquired at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] aio_poll fs/aio.c:1772 [inline] __io_submit_one fs/aio.c:1875 [inline] io_submit_one+0xedf/0x1cf0 fs/aio.c:1908 __do_sys_io_submit fs/aio.c:1953 [inline] __se_sys_io_submit fs/aio.c:1923 [inline] __x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe the dependencies between the lock to be acquired and SOFTIRQ-irq-unsafe lock: -> (&fiq->waitq){+.+.} { HARDIRQ-ON-W at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] flush_bg_queue+0x1f3/0x3c0 fs/fuse/dev.c:415 fuse_request_queue_background+0x2d1/0x580 fs/fuse/dev.c:676 fuse_request_send_background+0x58/0x120 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:989 [inline] fuse_fill_super+0x13bb/0x1730 fs/fuse/inode.c:1214 mount_nodev+0x68/0x110 fs/super.c:1392 fuse_mount+0x2d/0x40 fs/fuse/inode.c:1239 legacy_get_tree+0xf2/0x200 fs/fs_context.c:590 vfs_get_tree+0x123/0x450 fs/super.c:1481 do_new_mount fs/namespace.c:2610 [inline] do_mount+0x1436/0x2c40 fs/namespace.c:2932 ksys_mount+0xdb/0x150 fs/namespace.c:3148 __do_sys_mount fs/namespace.c:3162 [inline] __se_sys_mount fs/namespace.c:3159 [inline] __x64_sys_mount+0xbe/0x150 fs/namespace.c:3159 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe SOFTIRQ-ON-W at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] flush_bg_queue+0x1f3/0x3c0 fs/fuse/dev.c:415 fuse_request_queue_background+0x2d1/0x580 fs/fuse/dev.c:676 fuse_request_send_background+0x58/0x120 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:989 [inline] fuse_fill_super+0x13bb/0x1730 fs/fuse/inode.c:1214 mount_nodev+0x68/0x110 fs/super.c:1392 fuse_mount+0x2d/0x40 fs/fuse/inode.c:1239 legacy_get_tree+0xf2/0x200 fs/fs_context.c:590 vfs_get_tree+0x123/0x450 fs/super.c:1481 do_new_mount fs/namespace.c:2610 [inline] do_mount+0x1436/0x2c40 fs/namespace.c:2932 ksys_mount+0xdb/0x150 fs/namespace.c:3148 __do_sys_mount fs/namespace.c:3162 [inline] __se_sys_mount fs/namespace.c:3159 [inline] __x64_sys_mount+0xbe/0x150 fs/namespace.c:3159 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe INITIAL USE at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] flush_bg_queue+0x1f3/0x3c0 fs/fuse/dev.c:415 fuse_request_queue_background+0x2d1/0x580 fs/fuse/dev.c:676 fuse_request_send_background+0x58/0x120 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:989 [inline] fuse_fill_super+0x13bb/0x1730 fs/fuse/inode.c:1214 mount_nodev+0x68/0x110 fs/super.c:1392 fuse_mount+0x2d/0x40 fs/fuse/inode.c:1239 legacy_get_tree+0xf2/0x200 fs/fs_context.c:590 vfs_get_tree+0x123/0x450 fs/super.c:1481 do_new_mount fs/namespace.c:2610 [inline] do_mount+0x1436/0x2c40 fs/namespace.c:2932 ksys_mount+0xdb/0x150 fs/namespace.c:3148 __do_sys_mount fs/namespace.c:3162 [inline] __se_sys_mount fs/namespace.c:3159 [inline] __x64_sys_mount+0xbe/0x150 fs/namespace.c:3159 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe } ... key at: [] __key.43450+0x0/0x40 ... acquired at: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] aio_poll fs/aio.c:1772 [inline] __io_submit_one fs/aio.c:1875 [inline] io_submit_one+0xedf/0x1cf0 fs/aio.c:1908 __do_sys_io_submit fs/aio.c:1953 [inline] __se_sys_io_submit fs/aio.c:1923 [inline] __x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe stack backtrace: CPU: 0 PID: 13779 Comm: syz-executor2 Not tainted 5.0.0-rc4-next-20190131 #23 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+0x172/0x1f0 lib/dump_stack.c:113 print_bad_irq_dependency kernel/locking/lockdep.c:1573 [inline] check_usage.cold+0x60f/0x940 kernel/locking/lockdep.c:1605 check_irq_usage kernel/locking/lockdep.c:1650 [inline] check_prev_add_irq kernel/locking/lockdep_states.h:8 [inline] check_prev_add kernel/locking/lockdep.c:1860 [inline] check_prevs_add kernel/locking/lockdep.c:1968 [inline] validate_chain kernel/locking/lockdep.c:2339 [inline] __lock_acquire+0x1f12/0x4790 kernel/locking/lockdep.c:3320 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3826 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] aio_poll fs/aio.c:1772 [inline] __io_submit_one fs/aio.c:1875 [inline] io_submit_one+0xedf/0x1cf0 fs/aio.c:1908 __do_sys_io_submit fs/aio.c:1953 [inline] __se_sys_io_submit fs/aio.c:1923 [inline] __x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Reported-by: syzbot Cc: Christoph Hellwig Cc: Avi Kivity Cc: Miklos Szeredi Cc: Fixes: e8693bcfa0b4 ("aio: allow direct aio poll comletions for keyed wakeups") # v4.19 Signed-off-by: Miklos Szeredi [ bvanassche: added a comment ] Reluctantly-Acked-by: Christoph Hellwig Signed-off-by: Bart Van Assche Signed-off-by: Al Viro --- diff --git a/fs/aio.c b/fs/aio.c index b906ff70c90f..3083180a54c8 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1679,6 +1679,7 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, struct poll_iocb *req = container_of(wait, struct poll_iocb, wait); struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll); __poll_t mask = key_to_poll(key); + unsigned long flags; req->woken = true; @@ -1687,10 +1688,15 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, if (!(mask & req->events)) return 0; - /* try to complete the iocb inline if we can: */ - if (spin_trylock(&iocb->ki_ctx->ctx_lock)) { + /* + * Try to complete the iocb inline if we can. Use + * irqsave/irqrestore because not all filesystems (e.g. fuse) + * call this function with IRQs disabled and because IRQs + * have to be disabled before ctx_lock is obtained. + */ + if (spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) { list_del(&iocb->ki_list); - spin_unlock(&iocb->ki_ctx->ctx_lock); + spin_unlock_irqrestore(&iocb->ki_ctx->ctx_lock, flags); list_del_init(&req->wait.entry); aio_poll_complete(iocb, mask);