From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f71.google.com (mail-oo1-f71.google.com [209.85.161.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B89932D2495 for ; Mon, 16 Feb 2026 09:34:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771234477; cv=none; b=qU3Mhu4/nYk3TWEFAQU+Kx/6Goa0QQXCdNiciENFKqCFLselzi4ZtItK372V0BLK5xRmLtmMlRX3xO8B0nOVwookQIjsxfM6fmgQNLlFs4EqUw7R67sIlM5Cyl7ypCcCXctGox/FMa0AAKixRxZ1RQuk6WD3VMyT4Gs/qgq4sXs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771234477; c=relaxed/simple; bh=is7XHcm+pFf7lcMZnIi906vDeM6F5g671ozZAInD2z4=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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006d021491bc7-6785c22ac0amr3702669eaf.74.1771234474726; Mon, 16 Feb 2026 01:34:34 -0800 (PST) Date: Mon, 16 Feb 2026 01:34:34 -0800 In-Reply-To: <69906bdc.a70a0220.3c8f9c.0095.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6992e4aa.a70a0220.2c38d7.00e9.GAE@google.com> Subject: Re: [syzbot] [media?] KASAN: slab-use-after-free Read in dvb_frontend_release (3) From: syzbot To: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: c22e26bd0906 Merge tag 'landlock-7.0-rc1' of git://git.ker.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=16bcf6e6580000 kernel config: https://syzkaller.appspot.com/x/.config?x=6428d17febdfb14e dashboard link: https://syzkaller.appspot.com/bug?extid=ae466a728017ec940b41 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=15ce3652580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1121515a580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/b33c549157ca/disk-c22e26bd.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/34c7ded19553/vmlinux-c22e26bd.xz kernel image: https://storage.googleapis.com/syzbot-assets/66faec2158ed/bzImage-c22e26bd.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+ae466a728017ec940b41@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in dvb_frontend_release+0x410/0x4e0 drivers/media/dvb-core/dvb_frontend.c:2916 Read of size 4 at addr ffff88802b75b83c by task syz.0.18/5958 CPU: 1 UID: 0 PID: 5958 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 dvb_frontend_release+0x410/0x4e0 drivers/media/dvb-core/dvb_frontend.c:2916 __fput+0x45e/0xa80 fs/file_table.c:469 task_work_run+0x1d9/0x270 kernel/task_work.c:233 get_signal+0x11c3/0x1310 kernel/signal.c:2807 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline] exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline] do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fc97690bf79 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffed13b68c8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007ffed13b69b0 RCX: 00007fc97690bf79 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00000000000195a3 R08: 0000000000000001 R09: 0000000000000000 R10: 0000001b2d420000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fc976b85fac R14: 00007fc976b85fa8 R15: 00007fc976b85fa0 Allocated by task 1: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x3a6/0x690 mm/slub.c:5297 kmalloc_noprof include/linux/slab.h:962 [inline] kzalloc_noprof include/linux/slab.h:1204 [inline] dvb_register_device+0x2fd/0x2210 drivers/media/dvb-core/dvbdev.c:475 dvb_register_frontend+0x665/0x970 drivers/media/dvb-core/dvb_frontend.c:3051 vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:436 [inline] vidtv_bridge_probe+0x9aa/0xf80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:508 platform_probe+0xf9/0x190 drivers/base/platform.c:1446 call_driver_probe drivers/base/dd.c:-1 [inline] really_probe+0x267/0xaf0 drivers/base/dd.c:661 __driver_probe_device+0x18c/0x320 drivers/base/dd.c:803 driver_probe_device+0x4f/0x240 drivers/base/dd.c:833 __driver_attach+0x349/0x640 drivers/base/dd.c:1227 bus_for_each_dev+0x23e/0x2c0 drivers/base/bus.c:383 bus_add_driver+0x348/0x670 drivers/base/bus.c:715 driver_register+0x23a/0x320 drivers/base/driver.c:249 vidtv_bridge_init+0x28/0x50 drivers/media/test-drivers/vidtv/vidtv_bridge.c:598 do_one_initcall+0x250/0x840 init/main.c:1378 do_initcall_level+0x104/0x190 init/main.c:1440 do_initcalls+0x59/0xa0 init/main.c:1456 kernel_init_freeable+0x2a6/0x3d0 init/main.c:1688 kernel_init+0x1d/0x1d0 init/main.c:1578 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Freed by task 5958: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2670 [inline] slab_free mm/slub.c:6082 [inline] kfree+0x1c1/0x690 mm/slub.c:6399 dvb_free_device drivers/media/dvb-core/dvbdev.c:619 [inline] kref_put include/linux/kref.h:65 [inline] dvb_device_put drivers/media/dvb-core/dvbdev.c:632 [inline] dvb_generic_release+0x123/0x1c0 drivers/media/dvb-core/dvbdev.c:169 dvb_frontend_release+0x138/0x4e0 drivers/media/dvb-core/dvb_frontend.c:2914 __fput+0x45e/0xa80 fs/file_table.c:469 task_work_run+0x1d9/0x270 kernel/task_work.c:233 get_signal+0x11c3/0x1310 kernel/signal.c:2807 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline] exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline] do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88802b75b800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 60 bytes inside of freed 512-byte region [ffff88802b75b800, ffff88802b75ba00) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2b758 head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x80000000000040(head|node=0|zone=1) page_type: f5(slab) raw: 0080000000000040 ffff88813fe0dc80 dead000000000100 dead000000000122 raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000 head: 0080000000000040 ffff88813fe0dc80 dead000000000100 dead000000000122 head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000 head: 0080000000000002 ffffea0000add601 00000000ffffffff 00000000ffffffff head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000004 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2, tgid 2 (kthreadd), ts 14639760172, free_ts 0 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884 prep_new_page mm/page_alloc.c:1892 [inline] get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3950 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5245 alloc_slab_page mm/slub.c:3238 [inline] allocate_slab+0x77/0x660 mm/slub.c:3411 new_slab mm/slub.c:3469 [inline] refill_objects+0x334/0x3c0 mm/slub.c:7091 refill_sheaf mm/slub.c:2787 [inline] __pcs_replace_empty_main+0x328/0x5f0 mm/slub.c:4536 alloc_from_pcs mm/slub.c:4639 [inline] slab_alloc_node mm/slub.c:4773 [inline] __kmalloc_cache_noprof+0x44e/0x690 mm/slub.c:5292 kmalloc_noprof include/linux/slab.h:962 [inline] kzalloc_noprof include/linux/slab.h:1204 [inline] set_kthread_struct+0xbb/0x340 kernel/kthread.c:125 copy_process+0x128c/0x3d00 kernel/fork.c:2152 kernel_clone+0x249/0x7f0 kernel/fork.c:2654 kernel_thread+0x13f/0x1b0 kernel/fork.c:2715 create_kthread kernel/kthread.c:490 [inline] kthreadd+0x4ec/0x6e0 kernel/kthread.c:849 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 page_owner free stack trace missing Memory state around the buggy address: ffff88802b75b700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88802b75b780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88802b75b800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88802b75b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88802b75b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== --- 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.