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AJvYcCVmjsV1jWlVRmzJyWIdlHfe7EyT2IXcbwZ6tktksON6A6eJE0sKtKaVQ6JUHmeMMbDJrsr6nP/Sx8j9DTU=@vger.kernel.org X-Gm-Message-State: AOJu0YxpNSEjOmf/ifBtPHzLmTWpRf5seXL2zh8It6WjLN4vxs+d1cKK pneBe+8NJejJOBL1n7YhxAcClXWcEsLCkmLK+tusIWqLxhK0Mqu0kwYOO5p3mGr1JCOw6URdFC+ vlHMAI9r+juCcZeLAIgefvQAErYtQyd6cM2nTWX3XXn7a7jFzO4LkpRKeot8= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:3108:b0:679:dde1:c535 with SMTP id 006d021491bc7-67c0db0cd16mr4054754eaf.35.1773912542036; Thu, 19 Mar 2026 02:29:02 -0700 (PDT) Date: Thu, 19 Mar 2026 02:29:02 -0700 In-Reply-To: X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69bbc1de.050a0220.3a088d.000f.GAE@google.com> Subject: Re: [syzbot] [media?] [usb?] KASAN: slab-use-after-free Read in v4l2_open From: syzbot To: eadavis@qq.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: possible deadlock in em28xx_v4l2_open ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ v4l_id/6669 is trying to acquire lock: ffff888030ac9cd0 (&dev->lock#3){+.+.}-{4:4} , at: em28xx_v4l2_open+0xf0/0xa20 drivers/media/usb/em28xx/em28xx-video.c:2146 but task is already holding lock: ffffffff8f6a0520 (videodev_lock){+.+.}-{4:4}, at: v4l2_open+0x32/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:417 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (videodev_lock ){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 __video_register_device+0x54e/0x4d20 drivers/media/v4l2-core/v4l2-dev.c:1008 video_register_device include/media/v4l2-dev.h:390 [inline] em28xx_v4l2_init+0x1d32/0x2e70 drivers/media/usb/em28xx/em28xx-video.c:2788 em28xx_init_extension+0x120/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1117 process_one_work+0x9ab/0x1780 kernel/workqueue.c:3288 process_scheduled_works kernel/workqueue.c:3379 [inline] worker_thread+0xba8/0x11e0 kernel/workqueue.c:3465 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&dev->lock#3){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 em28xx_v4l2_open+0xf0/0xa20 drivers/media/usb/em28xx/em28xx-video.c:2146 v4l2_open+0x1b1/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:432 chrdev_open+0x4cd/0x5e0 fs/char_dev.c:411 do_dentry_open+0x785/0x14e0 fs/open.c:949 vfs_open+0x3b/0x340 fs/open.c:1081 do_open fs/namei.c:4693 [inline] path_openat+0x2e08/0x3860 fs/namei.c:4852 do_file_open+0x23e/0x4a0 fs/namei.c:4881 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(videodev_lock); lock(&dev->lock#3); lock(videodev_lock); lock(&dev->lock#3 ); *** DEADLOCK *** 1 lock held by v4l_id/6669: #0: ffffffff8f6a0520 (videodev_lock){+.+.}-{4:4}, at: v4l2_open+0x32/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:417 stack backtrace: CPU: 0 UID: 0 PID: 6669 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 em28xx_v4l2_open+0xf0/0xa20 drivers/media/usb/em28xx/em28xx-video.c:2146 v4l2_open+0x1b1/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:432 chrdev_open+0x4cd/0x5e0 fs/char_dev.c:411 do_dentry_open+0x785/0x14e0 fs/open.c:949 vfs_open+0x3b/0x340 fs/open.c:1081 do_open fs/namei.c:4693 [inline] path_openat+0x2e08/0x3860 fs/namei.c:4852 do_file_open+0x23e/0x4a0 fs/namei.c:4881 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f80328a7407 Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007ffdfce9d3b0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007f8033087880 RCX: 00007f80328a7407 RDX: 0000000000000000 RSI: 00007ffdfce9df1d RDI: ffffffffffffff9c RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 R13: 00007ffdfce9d600 R14: 00007f80331ee000 R15: 0000556e3f2c74d8 Tested on: commit: 8e42d251 Add linux-next specific files for 20260318 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=178e4a06580000 kernel config: https://syzkaller.appspot.com/x/.config?x=7f5b21566f9d8af6 dashboard link: https://syzkaller.appspot.com/bug?extid=1a7507a194fff09e5c44 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 patch: https://syzkaller.appspot.com/x/patch.diff?x=12e57352580000