[syzbot] [usb?] possible deadlock in chaoskey_open

[syzbot] [usb?] possible deadlock in chaoskey_open

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    4a9fe2a8ac53 dt-bindings: usb: dwc3-imx8mp: add compatible..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=1184d307980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4510af5d637450fb
dashboard link: https://syzkaller.appspot.com/bug?extid=5f1ce62e956b7b19610e
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1601d380580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1584479f980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/883c5319cb52/disk-4a9fe2a8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/caf4421ed2ef/vmlinux-4a9fe2a8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d8e3beb01d49/bzImage-4a9fe2a8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5f1ce62e956b7b19610e@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53 #0 Not tainted
------------------------------------------------------
syz-executor233/2673 is trying to acquire lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_open+0xdd/0x220 drivers/usb/misc/chaoskey.c:274

but task is already holding lock:
ffffffff899dadb0 (minor_rwsem){++++}-{3:3}, at: usb_open+0x23/0x220 drivers/usb/core/file.c:38

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (minor_rwsem){++++}-{3:3}:
       down_write+0x93/0x200 kernel/locking/rwsem.c:1577
       usb_deregister_dev+0x7c/0x1e0 drivers/usb/core/file.c:186
       chaoskey_disconnect+0xb7/0x2a0 drivers/usb/misc/chaoskey.c:236
       usb_unbind_interface+0x1e8/0x970 drivers/usb/core/driver.c:461
       device_remove drivers/base/dd.c:569 [inline]
       device_remove+0x122/0x170 drivers/base/dd.c:561
       __device_release_driver drivers/base/dd.c:1273 [inline]
       device_release_driver_internal+0x44a/0x610 drivers/base/dd.c:1296
       bus_remove_device+0x22f/0x420 drivers/base/bus.c:576
       device_del+0x396/0x9f0 drivers/base/core.c:3864
       usb_disable_device+0x36c/0x7f0 drivers/usb/core/message.c:1418
       usb_disconnect+0x2e1/0x920 drivers/usb/core/hub.c:2304
       hub_port_connect drivers/usb/core/hub.c:5361 [inline]
       hub_port_connect_change drivers/usb/core/hub.c:5661 [inline]
       port_event drivers/usb/core/hub.c:5821 [inline]
       hub_event+0x1bed/0x4f40 drivers/usb/core/hub.c:5903
       process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
       process_scheduled_works kernel/workqueue.c:3310 [inline]
       worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
       kthread+0x2c1/0x3a0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (chaoskey_list_lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain kernel/locking/lockdep.c:3904 [inline]
       __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202
       lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       chaoskey_open+0xdd/0x220 drivers/usb/misc/chaoskey.c:274
       usb_open+0x186/0x220 drivers/usb/core/file.c:47
       chrdev_open+0x237/0x6a0 fs/char_dev.c:414
       do_dentry_open+0x6cb/0x1390 fs/open.c:958
       vfs_open+0x82/0x3f0 fs/open.c:1088
       do_open fs/namei.c:3774 [inline]
       path_openat+0x1e6a/0x2d60 fs/namei.c:3933
       do_filp_open+0x1dc/0x430 fs/namei.c:3960
       do_sys_openat2+0x17a/0x1e0 fs/open.c:1415
       do_sys_open fs/open.c:1430 [inline]
       __do_sys_openat fs/open.c:1446 [inline]
       __se_sys_openat fs/open.c:1441 [inline]
       __x64_sys_openat+0x175/0x210 fs/open.c:1441
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(minor_rwsem);
                               lock(chaoskey_list_lock);
                               lock(minor_rwsem);
  lock(chaoskey_list_lock);

 *** DEADLOCK ***

1 lock held by syz-executor233/2673:
 #0: ffffffff899dadb0 (minor_rwsem){++++}-{3:3}, at: usb_open+0x23/0x220 drivers/usb/core/file.c:38

stack backtrace:
CPU: 1 UID: 0 PID: 2673 Comm: syz-executor233 Not tainted 6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x41c/0x610 kernel/locking/lockdep.c:2074
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain kernel/locking/lockdep.c:3904 [inline]
 __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
 chaoskey_open+0xdd/0x220 drivers/usb/misc/chaoskey.c:274
 usb_open+0x186/0x220 drivers/usb/core/file.c:47
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x6cb/0x1390 fs/open.c:958
 vfs_open+0x82/0x3f0 fs/open.c:1088
 do_open fs/namei.c:3774 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3933
 do_filp_open+0x1dc/0x430 fs/namei.c:3960
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1415
 do_sys_open fs/open.c:1430 [inline]
 __do_sys_openat fs/open.c:1446 [inline]
 __se_sys_openat fs/open.c:1441 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1441
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fab087d4e91
Code: 75 57 89 f0 25 00 00 41 00 3d 00 00 41 00 74 49 80 3d fa a1 07 00 00 74 6d 89 da 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 93 00 00 00 48 8b 54 24 28 64 48 2b 14 25
RSP: 002b:00007ffe8b2c7190 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fab087d4e91
RDX: 0000000000000002 RSI: 00007ffe8b2c7210 RDI: 00000000ffffff9c
RBP: 00007ffe8b2c7210 R08: 000000000000000f R09: 00007ffe8b2c6fa7
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffe8b2c72cc
R13: 00007ffe8b2c7300 R14: 00007ffe8b2c72e0 R15: 0000000000000002
 </TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this issue. See:
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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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If you want to overwrite report's subsystems, reply with:
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#syz undup

Re: [usb?] possible deadlock in chaoskey_open

[Edward Adam Davis]

delay get the chaoskey_list_lock, avoid to circular locking dependency

#syz test

diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c
index e8b63df5f975..17e29c6e878b 100644
--- a/drivers/usb/misc/chaoskey.c
+++ b/drivers/usb/misc/chaoskey.c
@@ -232,10 +232,10 @@ static void chaoskey_disconnect(struct usb_interface *interface)
 	if (dev->hwrng_registered)
 		hwrng_unregister(&dev->hwrng);
 
-	mutex_lock(&chaoskey_list_lock);
 	usb_deregister_dev(interface, &chaoskey_class);
 
 	usb_set_intfdata(interface, NULL);
+	mutex_lock(&chaoskey_list_lock);
 	mutex_lock(&dev->lock);
 
 	dev->present = false;

Re: [syzbot] [usb?] possible deadlock in chaoskey_open

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in chaoskey_release

============================================
WARNING: possible recursive locking detected
6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53-dirty #0 Not tainted
--------------------------------------------
syz.1.16/6532 is trying to acquire lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x15d/0x2c0 drivers/usb/misc/chaoskey.c:322

but task is already holding lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x7f/0x2c0 drivers/usb/misc/chaoskey.c:299

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(chaoskey_list_lock);
  lock(chaoskey_list_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz.1.16/6532:
 #0: ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x7f/0x2c0 drivers/usb/misc/chaoskey.c:299

stack backtrace:
CPU: 1 UID: 0 PID: 6532 Comm: syz.1.16 Not tainted 6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_deadlock_bug+0x2e3/0x410 kernel/locking/lockdep.c:3037
 check_deadlock kernel/locking/lockdep.c:3089 [inline]
 validate_chain kernel/locking/lockdep.c:3891 [inline]
 __lock_acquire+0x2185/0x3ce0 kernel/locking/lockdep.c:5202
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
 chaoskey_release+0x15d/0x2c0 drivers/usb/misc/chaoskey.c:322
 __fput+0x3f6/0xb60 fs/file_table.c:431
 task_work_run+0x14e/0x250 kernel/task_work.c:228
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x24e/0x260 kernel/entry/common.c:218
 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f35b167dff9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe690a74c8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 000000000001c363 RCX: 00007f35b167dff9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f35b1837a80 R08: 0000000000000001 R09: 00007ffe690a77bf
R10: 00007f35b14fa000 R11: 0000000000000246 R12: 000000000001cf4f
R13: 00007ffe690a75d0 R14: 0000000000000bea R15: ffffffffffffffff
 </TASK>


Tested on:

commit:         4a9fe2a8 dt-bindings: usb: dwc3-imx8mp: add compatible..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=15b89f9f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4510af5d637450fb
dashboard link: https://syzkaller.appspot.com/bug?extid=5f1ce62e956b7b19610e
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14adf707980000

Re: [usb?] possible deadlock in chaoskey_open

[Edward Adam Davis]

delay get the chaoskey_list_lock, avoid to circular locking dependency
chaoskey_release has a wrong logic lock for chaoskey_list_lock, it need unlock.

#syz test

diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c
index e8b63df5f975..225863321dc4 100644
--- a/drivers/usb/misc/chaoskey.c
+++ b/drivers/usb/misc/chaoskey.c
@@ -232,10 +232,10 @@ static void chaoskey_disconnect(struct usb_interface *interface)
 	if (dev->hwrng_registered)
 		hwrng_unregister(&dev->hwrng);
 
-	mutex_lock(&chaoskey_list_lock);
 	usb_deregister_dev(interface, &chaoskey_class);
 
 	usb_set_intfdata(interface, NULL);
+	mutex_lock(&chaoskey_list_lock);
 	mutex_lock(&dev->lock);
 
 	dev->present = false;
@@ -319,7 +319,7 @@ static int chaoskey_release(struct inode *inode, struct file *file)
 bail:
 	mutex_unlock(&dev->lock);
 destruction:
-	mutex_lock(&chaoskey_list_lock);
+	mutex_unlock(&chaoskey_list_lock);
 	usb_dbg(interface, "release success");
 	return rv;
 }

Re: [syzbot] [usb?] possible deadlock in chaoskey_open

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+5f1ce62e956b7b19610e@syzkaller.appspotmail.com
Tested-by: syzbot+5f1ce62e956b7b19610e@syzkaller.appspotmail.com

Tested on:

commit:         4a9fe2a8 dt-bindings: usb: dwc3-imx8mp: add compatible..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=12a49327980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4510af5d637450fb
dashboard link: https://syzkaller.appspot.com/bug?extid=5f1ce62e956b7b19610e
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11f89f9f980000

Note: testing is done by a robot and is best-effort only.