[syzbot] [media?] general protection fault in vidtv_s302m_encode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3b5f4b83c4ab Merge tag 'for-7.2-rc5-tag' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11068aea580000
kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=e9ce4d4ff55ba65e3980
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f99ca00b02a2/disk-3b5f4b83.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5caff5208bfc/vmlinux-3b5f4b83.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c0e941f5f816/bzImage-3b5f4b83.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e9ce4d...@syzkaller.appspotmail.com

kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 5713 Comm: kworker/0:5 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: events vidtv_mux_tick
RIP: 0010:vidtv_s302m_encode+0x269/0x1860 drivers/media/test-drivers/vidtv/vidtv_s302m.c:414
Code: 31 aa f9 31 ff 89 de e8 95 2b aa f9 84 db 0f 85 37 0d 00 00 e8 78 31 aa f9 4c 89 e2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e e7 14 00 00 48 8b 44 24 08 41
RSP: 0018:ffffc9000454f830 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000400
RDX: 0000000000000000 RSI: ffffffff88602ec8 RDI: ffff88813fe238c0
RBP: 0000000000000000 R08: 0000000000000dc0 R09: 00000000ffffffff
R10: ffffffff8edee673 R11: 0000000000000001 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff888076157200 R15: ffff88802e6f2000
FS: 0000000000000000(0000) GS:ffff888123ddc000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f89c38f7ff8 CR3: 0000000038e49000 CR4: 00000000003526f0
Call Trace:
<TASK>
vidtv_mux_poll_encoders drivers/media/test-drivers/vidtv/vidtv_mux.c:339 [inline]
vidtv_mux_tick+0x4e4/0x1460 drivers/media/test-drivers/vidtv/vidtv_mux.c:416
process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
process_scheduled_works kernel/workqueue.c:3405 [inline]
worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:vidtv_s302m_encode+0x269/0x1860 drivers/media/test-drivers/vidtv/vidtv_s302m.c:414
Code: 31 aa f9 31 ff 89 de e8 95 2b aa f9 84 db 0f 85 37 0d 00 00 e8 78 31 aa f9 4c 89 e2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e e7 14 00 00 48 8b 44 24 08 41
----------------
Code disassembly (best guess):
0: 31 aa f9 31 ff 89 xor %ebp,-0x7600ce07(%rdx)
6: de e8 fsubrp %st,%st(0)
8: 95 xchg %eax,%ebp
9: 2b aa f9 84 db 0f sub 0xfdb84f9(%rdx),%ebp
f: 85 37 test %esi,(%rdi)
11: 0d 00 00 e8 78 or $0x78e80000,%eax
16: 31 aa f9 4c 89 e2 xor %ebp,-0x1d76b307(%rdx)
1c: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
23: fc ff df
26: 48 c1 ea 03 shr $0x3,%rdx
* 2a: 0f b6 04 02 movzbl (%rdx,%rax,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 74 08 je 0x3a
32: 3c 03 cmp $0x3,%al
34: 0f 8e e7 14 00 00 jle 0x1521
3a: 48 8b 44 24 08 mov 0x8(%rsp),%rax
3f: 41 rex.B


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