On Mon, Sep 16, 2019 at 02:42:06PM -0700, syzbot wrote: > syzbot has found a reproducer for the following crash on: > > HEAD commit: f0df5c1b usb-fuzzer: main usb gadget fuzzer driver > git tree: https://github.com/google/kasan.git usb-fuzzer > console output: https://syzkaller.appspot.com/x/log.txt?x=175cdb95600000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5 > dashboard link: https://syzkaller.appspot.com/bug?extid=f9549f5ee8a5416f0b95 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13961369600000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=139c811d600000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+f9549f5ee8a5416f0b95@xxxxxxxxxxxxxxxxxxxxxxxxx > > usb 1-1: config 0 descriptor?? > legousbtower 1-1:0.219: LEGO USB Tower firmware version is 129.136 build > 65535 > legousbtower 1-1:0.219: LEGO USB Tower #-160 now attached to major 180 > minor 0 > usb 1-1: USB disconnect, device number 2 > ====================================================== > WARNING: possible circular locking dependency detected > 5.3.0-rc7+ #0 Not tainted > ------------------------------------------------------ > kworker/0:1/12 is trying to acquire lock: > 0000000098630ee4 (minor_rwsem){++++}, at: usb_deregister_dev+0x95/0x230 > drivers/usb/core/file.c:239 > > but task is already holding lock: > 00000000d9ad5b6f (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300 > drivers/usb/misc/legousbtower.c:945 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (open_disc_mutex){+.+.}: > __mutex_lock_common kernel/locking/mutex.c:930 [inline] > __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1077 > tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335 > usb_open+0x1df/0x270 drivers/usb/core/file.c:48 > chrdev_open+0x219/0x5c0 fs/char_dev.c:414 > do_dentry_open+0x494/0x1120 fs/open.c:797 > do_last fs/namei.c:3416 [inline] > path_openat+0x1430/0x3f50 fs/namei.c:3533 > do_filp_open+0x1a1/0x280 fs/namei.c:3563 > do_sys_open+0x3c0/0x580 fs/open.c:1089 > do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > -> #0 (minor_rwsem){++++}: > check_prev_add kernel/locking/lockdep.c:2405 [inline] > check_prevs_add kernel/locking/lockdep.c:2507 [inline] > validate_chain kernel/locking/lockdep.c:2897 [inline] > __lock_acquire+0x1f7c/0x3b50 kernel/locking/lockdep.c:3880 > lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412 > down_write+0x92/0x150 kernel/locking/rwsem.c:1500 > usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239 > tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951 > usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423 > __device_release_driver drivers/base/dd.c:1134 [inline] > device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1165 > bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:556 > device_del+0x420/0xb10 drivers/base/core.c:2339 > usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237 > usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199 > hub_port_connect drivers/usb/core/hub.c:4949 [inline] > hub_port_connect_change drivers/usb/core/hub.c:5213 [inline] > port_event drivers/usb/core/hub.c:5359 [inline] > hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441 > process_one_work+0x92b/0x1530 kernel/workqueue.c:2269 > worker_thread+0x96/0xe20 kernel/workqueue.c:2415 > kthread+0x318/0x420 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > > other info that might help us debug this: > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(open_disc_mutex); > lock(minor_rwsem); > lock(open_disc_mutex); > lock(minor_rwsem); > > *** DEADLOCK *** This should be fixed by the below patch. Looks like we may have a similar issue in a few more drivers. Fixing them up next. Johan #syz test: https://github.com/google/kasan.git f0df5c1b >From c2c2800f2687be963acc222045c8fd89f3877642 Mon Sep 17 00:00:00 2001 From: Johan Hovold <johan@xxxxxxxxxx> Date: Tue, 17 Sep 2019 12:32:22 +0200 Subject: [PATCH] USB: legousbtower: fix deadlock on disconnect Fix a potential deadlock if disconnect races with open. Since commit d4ead16f50f9 ("USB: prevent char device open/deregister race") core holds an rw-semaphore while open is called and when releasing the minor number during deregistration. This can lead to an ABBA deadlock if a driver takes a lock in open which it also holds during deregistration. This effectively reverts commit 78663ecc344b ("USB: disconnect open race in legousbtower") which needlessly introduced this issue after a generic fix for this race had been added to core by commit d4ead16f50f9 ("USB: prevent char device open/deregister race"). Fixes: 78663ecc344b ("USB: disconnect open race in legousbtower") Cc: stable <stable@xxxxxxxxxxxxxxx> # 2.6.24 Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Cc: Oliver Neukum <oneukum@xxxxxxxx> Reported-by: syzbot+f9549f5ee8a5416f0b95@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> --- drivers/usb/misc/legousbtower.c | 19 ++----------------- 1 file changed, 2 insertions(+), 17 deletions(-) diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c index 006cf13b2199..c125f03436a1 100644 --- a/drivers/usb/misc/legousbtower.c +++ b/drivers/usb/misc/legousbtower.c @@ -179,7 +179,6 @@ static const struct usb_device_id tower_table[] = { }; MODULE_DEVICE_TABLE (usb, tower_table); -static DEFINE_MUTEX(open_disc_mutex); #define LEGO_USB_TOWER_MINOR_BASE 160 @@ -332,18 +331,14 @@ static int tower_open (struct inode *inode, struct file *file) goto exit; } - mutex_lock(&open_disc_mutex); dev = usb_get_intfdata(interface); - if (!dev) { - mutex_unlock(&open_disc_mutex); retval = -ENODEV; goto exit; } /* lock this device */ if (mutex_lock_interruptible(&dev->lock)) { - mutex_unlock(&open_disc_mutex); retval = -ERESTARTSYS; goto exit; } @@ -351,12 +346,10 @@ static int tower_open (struct inode *inode, struct file *file) /* allow opening only once */ if (dev->open_count) { - mutex_unlock(&open_disc_mutex); retval = -EBUSY; goto unlock_exit; } dev->open_count = 1; - mutex_unlock(&open_disc_mutex); /* reset the tower */ result = usb_control_msg (dev->udev, @@ -423,10 +416,9 @@ static int tower_release (struct inode *inode, struct file *file) if (dev == NULL) { retval = -ENODEV; - goto exit_nolock; + goto exit; } - mutex_lock(&open_disc_mutex); if (mutex_lock_interruptible(&dev->lock)) { retval = -ERESTARTSYS; goto exit; @@ -456,10 +448,7 @@ static int tower_release (struct inode *inode, struct file *file) unlock_exit: mutex_unlock(&dev->lock); - exit: - mutex_unlock(&open_disc_mutex); -exit_nolock: return retval; } @@ -910,7 +899,6 @@ static int tower_probe (struct usb_interface *interface, const struct usb_device if (retval) { /* something prevented us from registering this driver */ dev_err(idev, "Not able to get a minor for this device.\n"); - usb_set_intfdata (interface, NULL); goto error; } dev->minor = interface->minor; @@ -942,16 +930,13 @@ static void tower_disconnect (struct usb_interface *interface) int minor; dev = usb_get_intfdata (interface); - mutex_lock(&open_disc_mutex); - usb_set_intfdata (interface, NULL); minor = dev->minor; - /* give back our minor */ + /* give back our minor and prevent further open() */ usb_deregister_dev (interface, &tower_class); mutex_lock(&dev->lock); - mutex_unlock(&open_disc_mutex); /* if the device is not opened, then we clean up right now */ if (!dev->open_count) { -- 2.23.0
