[syzbot] [i2c?] [usb?] WARNING: ODEBUG bug in i2c_device_remove (2)

[syzbot] [i2c?] [usb?] WARNING: ODEBUG bug in i2c_device_remove (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    c7275b05bc42 Add linux-next specific files for 20260417
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1782f4ce580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=10db2bdce6adb49e
dashboard link: https://syzkaller.appspot.com/bug?extid=019ced393ab913002b75
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10b79906580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16688cf2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ffefe34549f8/disk-c7275b05.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f679e5d59c0c/vmlinux-c7275b05.xz
kernel image: https://storage.googleapis.com/syzbot-assets/714f96953b57/bzImage-c7275b05.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+019ced393ab913002b75@syzkaller.appspotmail.com

usb 1-1: DVB: registering adapter 1 frontend 0 (Realtek RTL2832 (DVB-T))...
dvbdev: dvb_create_media_entity: media entity 'Realtek RTL2832 (DVB-T)' registered.
DVB: Unable to find symbol r820t_attach()
------------[ cut here ]------------
ODEBUG: free active (active state 0) object: ffff8880258626e8 object type: timer_list hint: rtl2832_i2c_gate_work+0x0/0x100 drivers/media/dvb-frontends/rtl2832.c:-1
WARNING: lib/debugobjects.c:632 at debug_print_object lib/debugobjects.c:629 [inline], CPU#1: kworker/1:2/821
WARNING: lib/debugobjects.c:632 at __debug_check_no_obj_freed lib/debugobjects.c:1116 [inline], CPU#1: kworker/1:2/821
WARNING: lib/debugobjects.c:632 at debug_check_no_obj_freed+0x405/0x550 lib/debugobjects.c:1146, CPU#1: kworker/1:2/821
Modules linked in:
CPU: 1 UID: 0 PID: 821 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: usb_hub_wq hub_event
RIP: 0010:debug_print_object lib/debugobjects.c:629 [inline]
RIP: 0010:__debug_check_no_obj_freed lib/debugobjects.c:1116 [inline]
RIP: 0010:debug_check_no_obj_freed+0x44a/0x550 lib/debugobjects.c:1146
Code: 89 44 24 20 e8 87 40 6f fd 48 8b 44 24 20 4c 8b 4d 00 4c 89 ef 48 c7 c6 a0 61 ca 8b 48 c7 c2 20 67 ca 8b 8b 0c 24 4d 89 f8 50 <67> 48 0f b9 3a 48 83 c4 08 4c 8b 6c 24 18 48 b9 00 00 00 00 00 fc
RSP: 0018:ffffc90004fa67b8 EFLAGS: 00010246
RAX: ffffffff8767dab0 RBX: ffffffff99edac98 RCX: 0000000000000000
RDX: ffffffff8bca6720 RSI: ffffffff8bca61a0 RDI: ffffffff8fd9d990
RBP: ffffffff8b6f5560 R08: ffff8880258626e8 R09: ffffffff8b6f68e0
R10: dffffc0000000000 R11: ffffffff81b15270 R12: ffff888025862800
R13: ffffffff8fd9d990 R14: ffff888025862000 R15: ffff8880258626e8
FS:  0000000000000000(0000) GS:ffff888125b62000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2ec609ae9c CR3: 000000003956c000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 slab_free_hook mm/slub.c:2620 [inline]
 slab_free mm/slub.c:6246 [inline]
 kfree+0x13e/0x6c0 mm/slub.c:6561
 i2c_device_remove+0x88/0x220 drivers/i2c/i2c-core-base.c:631
 device_remove drivers/base/dd.c:619 [inline]
 __device_release_driver drivers/base/dd.c:1352 [inline]
 device_release_driver_internal+0x46f/0x870 drivers/base/dd.c:1375
 bus_remove_device+0x45a/0x570 drivers/base/bus.c:657
 device_del+0x52b/0x900 drivers/base/core.c:3895
 device_unregister+0x21/0xf0 drivers/base/core.c:3936
 rtl28xxu_frontend_detach+0x168/0x210 drivers/media/usb/dvb-usb-v2/rtl28xxu.c:1105
 dvb_usbv2_adapter_frontend_exit drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:733 [inline]
 dvb_usbv2_adapter_exit drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:830 [inline]
 dvb_usbv2_exit+0x44c/0xb80 drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:844
 dvb_usbv2_probe+0x4c0/0x3c20 drivers/media/usb/dvb-usb-v2/dvb_usb_core.c:994
 usb_probe_interface+0x659/0xc70 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x267/0xaf0 drivers/base/dd.c:709
 __driver_probe_device+0x1ef/0x380 drivers/base/dd.c:871
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:901
 __device_attach_driver+0x279/0x430 drivers/base/dd.c:1029
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c8/0x450 drivers/base/dd.c:1101
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1156
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:613
 device_add+0x7e9/0xbb0 drivers/base/core.c:3706
 usb_set_configuration+0x1a87/0x2110 drivers/usb/core/message.c:2268
 usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
 usb_probe_device+0x1c4/0x3b0 drivers/usb/core/driver.c:291
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x267/0xaf0 drivers/base/dd.c:709
 __driver_probe_device+0x1ef/0x380 drivers/base/dd.c:871
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:901
 __device_attach_driver+0x279/0x430 drivers/base/dd.c:1029
 bus_for_each_drv+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c8/0x450 drivers/base/dd.c:1101
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1156
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:613
 device_add+0x7e9/0xbb0 drivers/base/core.c:3706
 usb_new_device+0x9f8/0x16e0 drivers/usb/core/hub.c:2695
 hub_port_connect drivers/usb/core/hub.c:5567 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x2a49/0x4f60 drivers/usb/core/hub.c:5953
 process_one_work+0x9a3/0x1710 kernel/workqueue.c:3312
 process_scheduled_works kernel/workqueue.c:3403 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3489
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
----------------
Code disassembly (best guess):
   0:	89 44 24 20          	mov    %eax,0x20(%rsp)
   4:	e8 87 40 6f fd       	call   0xfd6f4090
   9:	48 8b 44 24 20       	mov    0x20(%rsp),%rax
   e:	4c 8b 4d 00          	mov    0x0(%rbp),%r9
  12:	4c 89 ef             	mov    %r13,%rdi
  15:	48 c7 c6 a0 61 ca 8b 	mov    $0xffffffff8bca61a0,%rsi
  1c:	48 c7 c2 20 67 ca 8b 	mov    $0xffffffff8bca6720,%rdx
  23:	8b 0c 24             	mov    (%rsp),%ecx
  26:	4d 89 f8             	mov    %r15,%r8
  29:	50                   	push   %rax
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	48 83 c4 08          	add    $0x8,%rsp
  33:	4c 8b 6c 24 18       	mov    0x18(%rsp),%r13
  38:	48                   	rex.W
  39:	b9 00 00 00 00       	mov    $0x0,%ecx
  3e:	00 fc                	add    %bh,%ah


---
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.

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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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#syz undup

Forwarded: [PATCH] media: rtl2832: fix use-after-free in rtl2832_remove()

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH] media: rtl2832: fix use-after-free in rtl2832_remove()
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master


cancel_delayed_work_sync() is called before i2c_mux_del_adapters(),
but i2c_mux_del_adapters() internally performs I2C transfers which
trigger rtl2832_deselect(), which reschedules i2c_gate_work via
schedule_delayed_work(). This re-arms the timer after it has been
cancelled, causing a use-after-free when kfree(dev) is called and
the timer later fires on freed memory.

Fix this by calling i2c_mux_del_adapters() before
cancel_delayed_work_sync(). Once i2c_mux_del_adapters() completes,
no further I2C transfers can go through the mux, so rtl2832_deselect()
can never re-arm the timer again, making the cancellation truly final.

Reported-by: syzbot+019ced393ab913002b75@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=019ced393ab913002b75
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
 drivers/media/dvb-frontends/rtl2832.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/dvb-frontends/rtl2832.c b/drivers/media/dvb-frontends/rtl2832.c
index d8e1546aea5e..9898f729304a 100644
--- a/drivers/media/dvb-frontends/rtl2832.c
+++ b/drivers/media/dvb-frontends/rtl2832.c
@@ -1115,10 +1115,10 @@ static void rtl2832_remove(struct i2c_client *client)
 
 	dev_dbg(&client->dev, "\n");
 
-	cancel_delayed_work_sync(&dev->i2c_gate_work);
-
 	i2c_mux_del_adapters(dev->muxc);
 
+	cancel_delayed_work_sync(&dev->i2c_gate_work);
+
 	regmap_exit(dev->regmap);
 
 	kfree(dev);
-- 
2.43.0

Forwarded: [PATCH] media: rtl2832: fix use-after-free in rtl2832_remove()

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH] media: rtl2832: fix use-after-free in rtl2832_remove()
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master


cancel_delayed_work_sync() is called before i2c_mux_del_adapters()
in rtl2832_remove(). If i2c_mux_del_adapters() triggers any I2C
transfers through the mux adapter, rtl2832_deselect() will be called
which reschedules i2c_gate_work via schedule_delayed_work(). This
re-arms the timer after it was cancelled, causing a use-after-free
when kfree(dev) is called and the timer later fires on freed memory.

Fix this by moving cancel_delayed_work_sync() to after
i2c_mux_del_adapters(), ensuring the cancellation is the last
operation before kfree(dev).

Reported-by: syzbot+019ced393ab913002b75@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=019ced393ab913002b75
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
 drivers/media/dvb-frontends/rtl2832.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/media/dvb-frontends/rtl2832.c b/drivers/media/dvb-frontends/rtl2832.c
index d8e1546aea5e..ce3326feaa7d 100644
--- a/drivers/media/dvb-frontends/rtl2832.c
+++ b/drivers/media/dvb-frontends/rtl2832.c
@@ -821,6 +821,9 @@ static int rtl2832_deselect(struct i2c_mux_core *muxc, u32 chan_id)
 {
 	struct rtl2832_dev *dev = i2c_mux_priv(muxc);
 
+	pr_err("rtl2832_deselect called from: %pS\n",
+           __builtin_return_address(0));
+
 	schedule_delayed_work(&dev->i2c_gate_work, usecs_to_jiffies(100));
 	return 0;
 }
@@ -1113,12 +1116,18 @@ static void rtl2832_remove(struct i2c_client *client)
 {
 	struct rtl2832_dev *dev = i2c_get_clientdata(client);
 
+	pr_err("rtl2832_remove: before cancel\n");
+
 	dev_dbg(&client->dev, "\n");
 
 	cancel_delayed_work_sync(&dev->i2c_gate_work);
 
+	pr_err("rtl2832_remove: before i2c_mux_del_adapters\n");
+
 	i2c_mux_del_adapters(dev->muxc);
 
+	pr_err("rtl2832_remove: before kfree\n");
+
 	regmap_exit(dev->regmap);
 
 	kfree(dev);
-- 
2.43.0