KASAN: use-after-free Read in dvb_frontend_release

Status: upstream: reported C repro on 2026/03/02 23:20
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+944142359d6049a49b15@syzkaller.appspotmail.com
First crash: 160d, last: 8d05h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/07/27 upstream (ToT) f5098b6bae76 C [report] KASAN: slab-use-after-free Read in dvb_frontend_release
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in dvb_frontend_release origin:lts-only 19 syz, C error 14 35d 153d 0/3 upstream: reported C repro on 2026/03/09 12:55
upstream KASAN: slab-use-after-free Read in dvb_frontend_release (3) prio:high media 19 syz, C error 260 1d22h 176d 0/29 upstream: reported C repro on 2026/02/14 12:34
linux-6.6 KASAN: slab-use-after-free Read in dvb_frontend_release origin:upstream 19 syz, C error 4 74d 181d 0/2 upstream: reported C repro on 2026/02/09 03:58
upstream KASAN: slab-use-after-free Read in dvb_frontend_release (2) media 19 3 351d 347d 0/29 auto-obsoleted due to no activity on 2025/11/21 10:00
upstream KASAN: slab-use-after-free Read in dvb_frontend_release media 19 2 475d 484d 0/29 auto-obsoleted due to no activity on 2025/07/20 03:14
▶ ▼ Last patch testing requests (5)
Created Duration User Patch Repo Result
2026/08/01 18:03 16m retest repro linux-5.15.y report log
2026/08/01 18:03 18m retest repro linux-5.15.y report log
2026/08/01 18:03 19m retest repro linux-5.15.y report log
2026/08/01 18:03 16m retest repro linux-5.15.y report log
2026/03/16 23:23 12m retest repro linux-5.15.y report log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in dvb_frontend_release+0x3f8/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2903
Read of size 4 at addr ffff88802941f63c by task syz.0.18/4310

CPU: 0 PID: 4310 Comm: syz.0.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 dvb_frontend_release+0x3f8/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2903
 __fput+0x212/0x8c0 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 get_signal+0x123e/0x12e0 kernel/signal.c:2673
 arch_do_signal_or_restart+0xe6/0x12a0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f83dbc68e59
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:00007ffc8c117e18 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffc8c117f00 RCX: 00007f83dbc68e59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000012f5a R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b30820000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f83dbef0fac R14: 00007f83dbef0fa8 R15: 00007f83dbef0fa0
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:607 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 dvb_register_device+0x300/0x1dc0 drivers/media/dvb-core/dvbdev.c:488
 dvb_register_frontend+0x629/0x900 drivers/media/dvb-core/dvb_frontend.c:3034
 vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:438 [inline]
 vidtv_bridge_probe+0x9c1/0xf30 drivers/media/test-drivers/vidtv/vidtv_bridge.c:510
 platform_probe+0x137/0x1c0 drivers/base/platform.c:1391
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x276/0xc70 drivers/base/dd.c:595
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:775
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:805
 __driver_attach+0x45d/0x660 drivers/base/dd.c:1184
 bus_for_each_dev+0x182/0x1f0 drivers/base/bus.c:303
 bus_add_driver+0x324/0x5d0 drivers/base/bus.c:620
 driver_register+0x32d/0x430 drivers/base/driver.c:240
 vidtv_bridge_init+0x39/0x70 drivers/media/test-drivers/vidtv/vidtv_bridge.c:602
 do_one_initcall+0x272/0x730 init/main.c:1315
 do_initcall_level+0x13d/0x1f0 init/main.c:1388
 do_initcalls+0x4b/0x90 init/main.c:1404
 kernel_init_freeable+0x3d5/0x560 init/main.c:1628
 kernel_init+0x19/0x1b0 init/main.c:1519
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 4310:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 dvb_free_device drivers/media/dvb-core/dvbdev.c:635 [inline]
 kref_put include/linux/kref.h:65 [inline]
 dvb_device_put drivers/media/dvb-core/dvbdev.c:650 [inline]
 dvb_generic_release+0x11c/0x1b0 drivers/media/dvb-core/dvbdev.c:183
 dvb_frontend_release+0x134/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2901
 __fput+0x212/0x8c0 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 get_signal+0x123e/0x12e0 kernel/signal.c:2673
 arch_do_signal_or_restart+0xe6/0x12a0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff88802941f600
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 60 bytes inside of
 256-byte region [ffff88802941f600, ffff88802941f700)
The buggy address belongs to the page:
page:ffffea0000a50780 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2941e
head:ffffea0000a50780 order:1 compound_mapcount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888016c41b40
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2789, ts 18984920308, free_ts 0
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x807/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc_trace+0xf9/0x290 mm/slub.c:3250
 kmalloc include/linux/slab.h:607 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 set_kthread_struct kernel/kthread.c:103 [inline]
 kthread+0x10a/0x520 kernel/kthread.c:296
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88802941f500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802941f580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802941f600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff88802941f680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802941f700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/12 12:00 linux-5.15.y c86c4726e7f0 d78ea535 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in dvb_frontend_release
2026/06/26 13:47 linux-5.15.y eceeec79dbc6 7ff32d8b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in dvb_frontend_release
2026/06/26 11:14 linux-5.15.y eceeec79dbc6 7ff32d8b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in dvb_frontend_release
2026/03/02 23:19 linux-5.15.y 3330a8d33e08 b9dd6534 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in dvb_frontend_release
2026/07/12 11:12 linux-5.15.y c86c4726e7f0 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in dvb_frontend_release
2026/06/27 01:56 linux-5.15.y eceeec79dbc6 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in dvb_frontend_release
* Struck through repros no longer work on HEAD.