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Fri, 28 Aug 2026 22:28:33 -0700 (PDT) From: Jeffin Philip To: syzbot+3157015c6bd85395cddc@syzkaller.appspotmail.com Cc: dwlsalmeida@gmail.com, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [media?] WARNING in vidtv_stop_feed Date: Sat, 29 Aug 2026 10:58:16 +0530 Message-ID: <20260829052816.23479-1-jeffinphilip14@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <6a90f648.1d9ded08.62e62.00e2.GAE@google.com> References: <6a90f648.1d9ded08.62e62.00e2.GAE@google.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Fri, Aug 28 2026, syzbot wrote: >------------[ cut here ]------------ >DEBUG_LOCKS_WARN_ON(lock->magic != lock) >WARNING: kernel/locking/mutex.c:625 at __mutex_lock_common kernel/locking/mutex.c:625 [inline], CPU>3: syz.3.334/7114 >WARNING: kernel/locking/mutex.c:625 at __mutex_lock+0x944/0x1bc0 kernel/locking/mutex.c:821, CPU>3: syz.3.334/7114 >Modules linked in: >CPU: 3 UID: 0 PID: 7114 Comm: syz.3.334 Tainted: G L syzkaller >0 PREEMPT(full) >Tainted: [L]=SOFTLOCKUP >Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 >RIP: 0010:__mutex_lock_common kernel/locking/mutex.c:625 [inline] >RIP: 0010:__mutex_lock+0x94b/0x1bc0 kernel/locking/mutex.c:821 >Code: 0f b6 14 11 38 d0 7c 08 84 d2 0f 85 b4 10 00 00 44 8b 05 b8 11 7a 05 45 85 c0 75 13 48 8d 3d 9c 16 7d 05 48 c7 c6 80 d3 ef 8b <67> 48 0f b9 3a 90 e9 1b f8 ff ff 4d 8d a7 f0 0a 00 00 4c 89 e7 e8 >RSP: 0000:ffffc90025f2fae0 EFLAGS: 00010246 >RAX: 0000000000000003 RBX: ffff888029f2d128 RCX: 1ffffffff22898cc >RDX: 0000000000000000 RSI: ffffffff8befd380 RDI: ffffffff9147cb50 >RBP: ffffc90025f2fc50 R08: 0000000000000000 R09: 0000000000000000 >R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 >R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000 >FS: 0000000000000000(0000) GS:ffff888096c84000(0063) knlGS:0000000057892480 >CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 >CR2: 00000000f544aff4 CR3: 00000000577a8000 CR4: 0000000000352ef0 >Call Trace: > > vidtv_stop_feed+0x75/0x2a0 drivers/media/test-drivers/vidtv/vidtv_bridge.c:256 > dmx_ts_feed_stop_filtering+0xe9/0x1d0 drivers/media/dvb-core/dvb_demux.c:780 > dvb_dmxdev_feed_stop.isra.0+0x162/0x270 drivers/media/dvb-core/dmxdev.c:494 > dvb_dmxdev_filter_stop+0x1d0/0x390 drivers/media/dvb-core/dmxdev.c:572 > dvb_dmxdev_filter_free drivers/media/dvb-core/dmxdev.c:856 [inline] > dvb_demux_release+0x92/0x560 drivers/media/dvb-core/dmxdev.c:1256 > __fput+0x3ff/0xb50 fs/file_table.c:512 > task_work_run+0x150/0x240 kernel/task_work.c:233 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > __exit_to_user_mode_loop kernel/entry/common.c:70 [inline] > exit_to_user_mode_loop+0x1d8/0x700 kernel/entry/common.c:101 > __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] > syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] > syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline] > __do_fast_syscall_32+0x59f/0x8b0 arch/x86/entry/syscall_32.c:294 > do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:316 > entry_SYSENTER_compat_after_hwframe+0x84/0x8e >RIP: 0023:0xf6ffefec >Code: Unable to access opcode bytes at 0xf6ffefc2. >RSP: 002b:00000000ffb45dfc EFLAGS: 00000202 ORIG_RAX: 00000000000001b4 >RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000000001e >RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 >RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 >R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 >R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > >---------------- >Code disassembly (best guess): > 0: 0f b6 14 11 movzbl (%rcx,%rdx,1),%edx > 4: 38 d0 cmp %dl,%al > 6: 7c 08 jl 0x10 > 8: 84 d2 test %dl,%dl > a: 0f 85 b4 10 00 00 jne 0x10c4 > 10: 44 8b 05 b8 11 7a 05 mov 0x57a11b8(%rip),%r8d > 0x57a11cf > 17: 45 85 c0 test %r8d,%r8d > 1a: 75 13 jne 0x2f > 1c: 48 8d 3d 9c 16 7d 05 lea 0x57d169c(%rip),%rdi > 0x57d16bf > 23: 48 c7 c6 80 d3 ef 8b mov $0xffffffff8befd380,%rsi >* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction > 2f: 90 nop > 30: e9 1b f8 ff ff jmp 0xfffff850 > 35: 4d 8d a7 f0 0a 00 00 lea 0xaf0(%r15),%r12 > 3c: 4c 89 e7 mov %r12,%rdi > 3f: e8 .byte 0xe8 I believe this is a extension of this crash[1]. Would consider marking it as invalid as it is a user-unreachable path said by Greg KH here[2] [1]: https://lore.kernel.org/all/6a8c451c.dbb3a75c.7844.0004.GAE@google.com/T/ [2]: https://lore.kernel.org/all/2026082737-traitor-shorter-a4cc@gregkh/ Thanks, Jeffin.