From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.167.200 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793774316; b=1j0pIo4TIHHklm9Hz39iVslkRdVlrMEXBNiv6IkwRyROLN7i8jXWeiKrq71C82SEthWz G7ktP18nPoz/JMLiQ2zuzq1lutBJVCRpePbgWWWsvybX7MApd1MJgaERlsPQJYnMjbLxc Z+BRsImPlnBs/Bs79j6MpHu+ssBd7Da7hiBO3UmNa0Mz8PY+cN70k2k45E2chlgRUHfvC jk8/0msQCCIKKw4afkB6GKhYCgr+H3vEGOCjv+jccn/qUZwEzt1nLvGOJh4cS0nYI1jNp Rvv4MLhlOrhyhw+NFOcmlHPDxRlcSkbFkFi3t+zP/XWln0UPkflzTq5Q1KyNaUqNl/g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793774316; h=DMARC-Filter:Received:X-Google-DKIM-Signature:X-Forwarded-Encrypted: X-Gm-Message-State:MIME-Version:X-Received:Date: X-Google-Appengine-App-Id:X-Google-Appengine-App-Id-Alias:Message-ID: Subject:From:To:Content-Type; bh=BqJvBGEmlOEUiMEuSomhKkkIhAEsRGhylpEaf3nKmLw=; b=NEqb7GPNesqRoTr+ypyQv7BGHJq9ToUyz0GjWQZcGTQqP4c0IxIM8TL4Ej7IXss2Ngde cRj8mKSqBlHOJb0aX2A7uH4b/FwY1jUMBf84UJGniFWLB/6fiqo2N7NfOV1ANmJWEyfB/ 2rT0SYl7TgZDcUPJKbnSSf00hGaW0kgQ5GNpWJBtUFFIJ1pTKrW0KZtcRp5d7WAvBqXRd ea9ZIkjz5RjZ2QjkNG4tt581XlY4luOh0J56M2lOmRPzPLDe5cpQWktEU6EMup38fQkt6 Im0uorSLLclhxuc6GldQ9EBYzDWR7u+Vy/hLAlLh1DMcdDXavJ9cizoEFs6C2eZNp1A== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.remote-ip=209.85.167.200 Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 05A22606A31B for ; Wed, 4 Nov 2026 06:38:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 05A22606A31B Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f200.google.com with SMTP id 5614622812f47-4c467e19391so654101b6e.3 for ; Tue, 03 Nov 2026 22:38:35 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793774315; x=1794379115; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=BqJvBGEmlOEUiMEuSomhKkkIhAEsRGhylpEaf3nKmLw=; b=OQNdTh2p3r/olDCTgeDeRBikhBPjvsdF82P7zrD8tj4/qSUc/G0DJucQ1sZ77yCDes rxS4oeR3GlmrzxJXYGOEe0QAe7zvfnnuhnREXzn2clsfIsaLvWh3NCmnKNXLVkLxXsHZ GzrVDhGvbfT2TX0aJgxjA5gSGjiHVs7mIExP6ODbz8OJcoaRQ6rGQx4xrhVFBJLIWZ+2 UDQit4Xj1tBrMTv3Ot33d/6+OWwhQzzDNslrCshvgR0ks/AWVtY+XvKN3q06Z9gB6Rms zBEA+GekgkLV5bvD3tHXXTlmktM4ZZ+cwmLtsglKFF3BrcSIInuTEopiy/QZTHjw9hXD CoGQ== X-Forwarded-Encrypted: i=1; AKwUvBzrRl7vE5SnSv96ZTQebltzlnsQjH5UPv3dyEdUKOLfjWKCYXFLeCyiD2LCm++DjLYPPG1stxF5bIIiuH4=@vger.kernel.org X-Gm-Message-State: APuU4Z9NBiw40/IaWMVSJE23vt2CLr94WWkf/o+yDS+/IHMDm6ddmWaF 2ItMqD6h064v4whxBuQkYYWfarU2eV9LBXp/OlWrBY4yzw9Yq8OFXjdwVlwkwe2ufF5VhuDEPWl hhrYTsvPACq9LKviDRTjYOYqfQhU2E1XYlMXEJ/5aV6qlD1+fGHwclPIKORs= X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Received: by 2002:a05:6808:14d3:b0:4e6:cc78:edc1 with SMTP id 5614622812f47-5640dd5fcffmr11061613b6e.42.1793774315044; Tue, 03 Nov 2026 22:38:35 -0800 (PST) Date: Tue, 03 Nov 2026 22:38:35 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6aead2eb.3c6f2eba.20048d.0000.GAE@google.com> Subject: [syzbot] [media?] [dri?] kernel BUG in sync_timeline_signal From: syzbot To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 6628e7d4c6b2 Linux 7.4-rc1 git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=13fa63f1580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1d2c97eac7d33533 dashboard link: https://syzkaller.appspot.com/bug?extid=cba1a1f459230395a076 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=134d2959580000 AI-generated root cause summary: In drivers/dma-buf/sw_sync.c, a race condition exists between dma_fence_put() and sync_timeline_signal(). When the last reference to a sync_pt fence is dropped, its refcount reaches 0 before dma_fence_release() -> timeline_fence_release() acquires obj->lock to remove the sync_pt from obj->pt_list. If sync_timeline_signal() runs concurrently under obj->lock, it iterates obj->pt_list and calls dma_fence_get() on the fence whose refcount is already 0, violating refcount invariants and causing a use-after-free / refcount addition-on-0 kernel crash. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=cba1a1f459230395a076 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+cba1a1f459230395a076@syzkaller.appspotmail.com refcount_t: addition on 0; use-after-free. ------------[ cut here ]------------ kernel BUG at lib/refcount.c:34! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 1 UID: 0 PID: 6018 Comm: syz-executor369 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026 RIP: 0010:refcount_warn_saturate.cold+0x12/0x14 lib/refcount.c:34 Code: 89 ea be 01 00 00 00 48 c7 c7 40 c1 c3 90 e8 0a 5a 01 00 e9 72 e3 02 04 e8 c0 54 d7 00 48 c7 c7 a0 4a 81 8c e8 04 85 eb ff 90 <0f> 0b e8 ac 54 d7 00 48 c7 c7 40 4b 81 8c e8 f0 84 eb ff 90 0f 0b RSP: 0018:ffffc90003e57cb8 EFLAGS: 00010086 RAX: 000000000000002a RBX: ffff88802d271570 RCX: 0000000000000000 RDX: 000000000000002a RSI: ffffffff81ebf219 RDI: fffff520007caf88 RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000 R10: ffffc90003e57a7f R11: 0000000000000001 R12: 0000000000000000 R13: dffffc0000000000 R14: ffff88802d271300 R15: ffffc90003e57d18 FS: 00007f83e74d26c0(0000) GS:ffff88812257d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f83e75a93c8 CR3: 00000000357c8000 CR4: 00000000003526f0 Call Trace: __refcount_add include/linux/refcount.h:289 [inline] __refcount_inc include/linux/refcount.h:366 [inline] refcount_inc include/linux/refcount.h:383 [inline] kref_get include/linux/kref.h:45 [inline] dma_fence_get include/linux/dma-fence.h:323 [inline] sync_timeline_signal+0x6d9/0x8a0 drivers/dma-buf/sw_sync.c:224 sw_sync_ioctl_inc drivers/dma-buf/sw_sync.c:405 [inline] sw_sync_ioctl+0x7b4/0x13f0 drivers/dma-buf/sw_sync.c:470 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f83e7507d5b Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00 RSP: 002b:00007f83e74d2100 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f83e7507d5b RDX: 00007f83e74d2170 RSI: 0000000040045701 RDI: 0000000000000003 RBP: 00000000000003d0 R08: 0000000000000000 R09: 00007f83e74d26c0 R10: 0000000000000008 R11: 0000000000000246 R12: 00007f83e74d2170 R13: 00000000000000f3 R14: 00007ffcce841440 R15: 00007ffcce841528 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:refcount_warn_saturate.cold+0x12/0x14 lib/refcount.c:34 Code: 89 ea be 01 00 00 00 48 c7 c7 40 c1 c3 90 e8 0a 5a 01 00 e9 72 e3 02 04 e8 c0 54 d7 00 48 c7 c7 a0 4a 81 8c e8 04 85 eb ff 90 <0f> 0b e8 ac 54 d7 00 48 c7 c7 40 4b 81 8c e8 f0 84 eb ff 90 0f 0b RSP: 0018:ffffc90003e57cb8 EFLAGS: 00010086 RAX: 000000000000002a RBX: ffff88802d271570 RCX: 0000000000000000 RDX: 000000000000002a RSI: ffffffff81ebf219 RDI: fffff520007caf88 RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000 R10: ffffc90003e57a7f R11: 0000000000000001 R12: 0000000000000000 R13: dffffc0000000000 R14: ffff88802d271300 R15: ffffc90003e57d18 FS: 00007f83e74d26c0(0000) GS:ffff88812257d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f83e75a93c8 CR3: 00000000357c8000 CR4: 00000000003526f0 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. 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 If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup