linux-kernel - [syzbot] [media?] WARNING: refcount bug in dvb_device

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Message-ID: <67ffa933.050a0220.243d89.0004.GAE@google.com>
Date: Wed, 16 Apr 2025 05:57:23 -0700
From: syzbot <syzbot+0aea3ca127fe06c384f7@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
	mchehab@...nel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [media?] WARNING: refcount bug in dvb_device_open

Hello,

syzbot found the following issue on:

HEAD commit:    e618ee89561b Merge tag 'spi-fix-v6.15-rc1' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=109b8a3f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7a4e108575159039
dashboard link: https://syzkaller.appspot.com/bug?extid=0aea3ca127fe06c384f7
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6e9ff64c0a63/disk-e618ee89.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5a0301cd26c2/vmlinux-e618ee89.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d51cf55acedf/bzImage-e618ee89.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0aea3ca127fe06c384f7@...kaller.appspotmail.com

------------[ cut here ]------------
refcount_t: saturated; leaking memory.
WARNING: CPU: 1 PID: 9920 at lib/refcount.c:22 refcount_warn_saturate+0xd4/0x210 lib/refcount.c:22
Modules linked in:
CPU: 1 UID: 0 PID: 9920 Comm: syz.5.1429 Not tainted 6.15.0-rc1-syzkaller-00288-ge618ee89561b #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:refcount_warn_saturate+0xd4/0x210 lib/refcount.c:22
Code: 7d a1 0b 31 ff 89 de e8 4a e5 ed fc 84 db 75 dc e8 61 ea ed fc c6 05 2f 7d a1 0b 01 90 48 c7 c7 40 fa f3 8b e8 ed 7b ad fc 90 <0f> 0b 90 90 eb bc e8 41 ea ed fc 0f b6 1d 10 7d a1 0b 31 ff 89 de
RSP: 0018:ffffc90002ee7908 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000cd2b000
RDX: 0000000000080000 RSI: ffffffff817ad005 RDI: 0000000000000001
RBP: ffff88802a664210 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff888033636a80
R13: ffffffff9afc7fa0 R14: ffff88802a2f28b0 R15: ffff88802a664210
FS:  00007f9f6790e6c0(0000) GS:ffff888124ab9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32715ff8 CR3: 0000000039f06000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __refcount_add include/linux/refcount.h:291 [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]
 dvb_device_get drivers/media/dvb-core/dvbdev.c:624 [inline]
 dvb_device_open+0x2ed/0x3b0 drivers/media/dvb-core/dvbdev.c:106
 chrdev_open+0x231/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x741/0x1c10 fs/open.c:956
 vfs_open+0x82/0x3f0 fs/open.c:1086
 do_open fs/namei.c:3845 [inline]
 path_openat+0x1e5e/0x2d40 fs/namei.c:4004
 do_filp_open+0x20b/0x470 fs/namei.c:4031
 do_sys_openat2+0x11b/0x1d0 fs/open.c:1429
 do_sys_open fs/open.c:1444 [inline]
 __do_sys_openat fs/open.c:1460 [inline]
 __se_sys_openat fs/open.c:1455 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1455
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9f66b8d169
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:00007f9f6790e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f9f66da5fa0 RCX: 00007f9f66b8d169
RDX: 0000000000000001 RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007f9f66c0e990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9f66da5fa0 R15: 00007ffdfcf6c128
 </TASK>


---
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