4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sean Young sean@mess.org
[ Upstream commit db5b15b74ed9a5c04bb808d18ffa2c773f5c18c0 ]
The locking in lirc needs improvement, but for now just fix this potential deadlock.
====================================================== [ INFO: possible circular locking dependency detected ] 4.10.0-rc1+ #1 Not tainted ------------------------------------------------------- bash/2502 is trying to acquire lock: (ir_raw_handler_lock){+.+.+.}, at: [<ffffffffc06f6a5e>] ir_raw_encode_scancode+0x3e/0xb0 [rc_core]
but task is already holding lock: (&dev->lock){+.+.+.}, at: [<ffffffffc06f511f>] store_filter+0x9f/0x240 [rc_core]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&dev->lock){+.+.+.}:
[<ffffffffa110adad>] lock_acquire+0xfd/0x200 [<ffffffffa1921327>] mutex_lock_nested+0x77/0x6d0 [<ffffffffc06f436a>] rc_open+0x2a/0x80 [rc_core] [<ffffffffc07114ca>] lirc_dev_fop_open+0xda/0x1e0 [lirc_dev] [<ffffffffa12975e0>] chrdev_open+0xb0/0x210 [<ffffffffa128eb5a>] do_dentry_open+0x20a/0x2f0 [<ffffffffa128ffcc>] vfs_open+0x4c/0x80 [<ffffffffa12a35ec>] path_openat+0x5bc/0xc00 [<ffffffffa12a5271>] do_filp_open+0x91/0x100 [<ffffffffa12903f0>] do_sys_open+0x130/0x220 [<ffffffffa12904fe>] SyS_open+0x1e/0x20 [<ffffffffa19278c1>] entry_SYSCALL_64_fastpath+0x1f/0xc2 -> #1 (lirc_dev_lock){+.+.+.}: [<ffffffffa110adad>] lock_acquire+0xfd/0x200 [<ffffffffa1921327>] mutex_lock_nested+0x77/0x6d0 [<ffffffffc0711f47>] lirc_register_driver+0x67/0x59b [lirc_dev] [<ffffffffc06db7f4>] ir_lirc_register+0x1f4/0x260 [ir_lirc_codec] [<ffffffffc06f6cac>] ir_raw_handler_register+0x7c/0xb0 [rc_core] [<ffffffffc0398010>] 0xffffffffc0398010 [<ffffffffa1002192>] do_one_initcall+0x52/0x1b0 [<ffffffffa11ef5c8>] do_init_module+0x5f/0x1fa [<ffffffffa11566b5>] load_module+0x2675/0x2b00 [<ffffffffa1156dcf>] SYSC_finit_module+0xdf/0x110 [<ffffffffa1156e1e>] SyS_finit_module+0xe/0x10 [<ffffffffa1003f5c>] do_syscall_64+0x6c/0x1f0 [<ffffffffa1927989>] return_from_SYSCALL_64+0x0/0x7a -> #0 (ir_raw_handler_lock){+.+.+.}: [<ffffffffa110a7b7>] __lock_acquire+0x10f7/0x1290 [<ffffffffa110adad>] lock_acquire+0xfd/0x200 [<ffffffffa1921327>] mutex_lock_nested+0x77/0x6d0 [<ffffffffc06f6a5e>] ir_raw_encode_scancode+0x3e/0xb0 [rc_core] [<ffffffffc0b0f492>] loop_set_wakeup_filter+0x62/0xbd [rc_loopback] [<ffffffffc06f522a>] store_filter+0x1aa/0x240 [rc_core] [<ffffffffa15e46f8>] dev_attr_store+0x18/0x30 [<ffffffffa13318e5>] sysfs_kf_write+0x45/0x60 [<ffffffffa1330b55>] kernfs_fop_write+0x155/0x1e0 [<ffffffffa1290797>] __vfs_write+0x37/0x160 [<ffffffffa12921f8>] vfs_write+0xc8/0x1e0 [<ffffffffa12936e8>] SyS_write+0x58/0xc0 [<ffffffffa19278c1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
other info that might help us debug this:
Chain exists of: ir_raw_handler_lock --> lirc_dev_lock --> &dev->lock
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&dev->lock); lock(lirc_dev_lock); lock(&dev->lock); lock(ir_raw_handler_lock);
*** DEADLOCK ***
4 locks held by bash/2502: #0: (sb_writers#4){.+.+.+}, at: [<ffffffffa12922c5>] vfs_write+0x195/0x1e0 #1: (&of->mutex){+.+.+.}, at: [<ffffffffa1330b1f>] kernfs_fop_write+0x11f/0x1e0 #2: (s_active#215){.+.+.+}, at: [<ffffffffa1330b28>] kernfs_fop_write+0x128/0x1e0 #3: (&dev->lock){+.+.+.}, at: [<ffffffffc06f511f>] store_filter+0x9f/0x240 [rc_core]
stack backtrace: CPU: 3 PID: 2502 Comm: bash Not tainted 4.10.0-rc1+ #1 Hardware name: /DG45ID, BIOS IDG4510H.86A.0135.2011.0225.1100 02/25/2011 Call Trace: dump_stack+0x86/0xc3 print_circular_bug+0x1be/0x210 __lock_acquire+0x10f7/0x1290 lock_acquire+0xfd/0x200 ? ir_raw_encode_scancode+0x3e/0xb0 [rc_core] ? ir_raw_encode_scancode+0x3e/0xb0 [rc_core] mutex_lock_nested+0x77/0x6d0 ? ir_raw_encode_scancode+0x3e/0xb0 [rc_core] ? loop_set_wakeup_filter+0x44/0xbd [rc_loopback] ir_raw_encode_scancode+0x3e/0xb0 [rc_core] loop_set_wakeup_filter+0x62/0xbd [rc_loopback] ? loop_set_tx_duty_cycle+0x70/0x70 [rc_loopback] store_filter+0x1aa/0x240 [rc_core] dev_attr_store+0x18/0x30 sysfs_kf_write+0x45/0x60 kernfs_fop_write+0x155/0x1e0 __vfs_write+0x37/0x160 ? rcu_read_lock_sched_held+0x4a/0x80 ? rcu_sync_lockdep_assert+0x2f/0x60 ? __sb_start_write+0x10c/0x220 ? vfs_write+0x195/0x1e0 ? security_file_permission+0x3b/0xc0 vfs_write+0xc8/0x1e0 SyS_write+0x58/0xc0 entry_SYSCALL_64_fastpath+0x1f/0xc2
Signed-off-by: Sean Young sean@mess.org Signed-off-by: Mauro Carvalho Chehab mchehab@s-opensource.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/media/rc/lirc_dev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/media/rc/lirc_dev.c +++ b/drivers/media/rc/lirc_dev.c @@ -446,6 +446,8 @@ int lirc_dev_fop_open(struct inode *inod return -ERESTARTSYS;
ir = irctls[iminor(inode)]; + mutex_unlock(&lirc_dev_lock); + if (!ir) { retval = -ENODEV; goto error; @@ -486,8 +488,6 @@ int lirc_dev_fop_open(struct inode *inod }
error: - mutex_unlock(&lirc_dev_lock); - nonseekable_open(inode, file);
return retval;