KASAN: slab-use-after-free Read in dvb_frontend_release

Status: upstream: reported C repro on 2026/02/09 03:58
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+c7c57465f74219389dc6@syzkaller.appspotmail.com
First crash: 168d, last: 61d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/05/28 upstream (ToT) 8fde5d1d47f6 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
upstream KASAN: slab-use-after-free Read in dvb_frontend_release (2) media 19 3 338d 334d 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 462d 471d 0/29 auto-obsoleted due to no activity on 2025/07/20 03:14
upstream KASAN: slab-use-after-free Read in dvb_frontend_release (3) prio:high media 19 C error 245 1h00m 163d 0/29 upstream: reported C repro on 2026/02/14 12:34
linux-5.15 KASAN: use-after-free Read in dvb_frontend_release origin:upstream 19 C error 6 15d 146d 0/3 upstream: reported C repro on 2026/03/02 23:20
linux-6.1 KASAN: use-after-free Read in dvb_frontend_release origin:lts-only 19 C error 14 21d 140d 0/3 upstream: reported C repro on 2026/03/09 12:55

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in dvb_frontend_release+0x3ff/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2921
Read of size 4 at addr ffff8880273b023c by task syz.0.18/5926

CPU: 0 PID: 5926 Comm: syz.0.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 dvb_frontend_release+0x3ff/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2921
 __fput+0x234/0x970 fs/file_table.c:384
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 get_signal+0x1235/0x13f0 kernel/signal.c:2678
 arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb7c079ce59
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:00007ffddb3ff5c8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffddb3ff6b0 RCX: 00007fb7c079ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000019de5 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b33c20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb7c0a15fac R14: 00007fb7c0a15fa8 R15: 00007fb7c0a15fa0
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 dvb_register_device+0x2fd/0x2210 drivers/media/dvb-core/dvbdev.c:475
 dvb_register_frontend+0x649/0x930 drivers/media/dvb-core/dvb_frontend.c:3056
 vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:438 [inline]
 vidtv_bridge_probe+0x9ab/0xf80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:510
 platform_probe+0x13b/0x1c0 drivers/base/platform.c:1404
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x25b/0xb20 drivers/base/dd.c:658
 __driver_probe_device+0x1ef/0x390 drivers/base/dd.c:820
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:850
 __driver_attach+0x44e/0x6e0 drivers/base/dd.c:1236
 bus_for_each_dev+0x235/0x2b0 drivers/base/bus.c:370
 bus_add_driver+0x340/0x630 drivers/base/bus.c:675
 driver_register+0x23a/0x310 drivers/base/driver.c:246
 vidtv_bridge_init+0x3d/0x70 drivers/media/test-drivers/vidtv/vidtv_bridge.c:600
 do_one_initcall+0x242/0x790 init/main.c:1249
 do_initcall_level+0x137/0x1f0 init/main.c:1311
 do_initcalls+0x69/0xd0 init/main.c:1327
 kernel_init_freeable+0x3ed/0x580 init/main.c:1564
 kernel_init+0x1d/0x1c0 init/main.c:1454
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Freed by task 5926:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1e0 mm/slub.c:3843
 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+0x123/0x1b0 drivers/media/dvb-core/dvbdev.c:169
 dvb_frontend_release+0x138/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2919
 __fput+0x234/0x970 fs/file_table.c:384
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 get_signal+0x1235/0x13f0 kernel/signal.c:2678
 arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff8880273b0200
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 60 bytes inside of
 freed 256-byte region [ffff8880273b0200, ffff8880273b0300)

The buggy address belongs to the physical page:
page:ffffea00009cec00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x273b0
head:ffffea00009cec00 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c41b40 dead000000000122 0000000000000000
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 1, tgid 1 (swapper/0), ts 19523995695, free_ts 0
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
 prep_new_page mm/page_alloc.c:1588 [inline]
 get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
 alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2118
 alloc_slab_page+0x5d/0x160 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5d/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x19e/0x250 mm/slub.c:3534
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 bus_add_driver+0x162/0x630 drivers/base/bus.c:659
 driver_register+0x23a/0x310 drivers/base/driver.c:246
 vidtv_bridge_init+0x3d/0x70 drivers/media/test-drivers/vidtv/vidtv_bridge.c:600
 do_one_initcall+0x242/0x790 init/main.c:1249
 do_initcall_level+0x137/0x1f0 init/main.c:1311
 do_initcalls+0x69/0xd0 init/main.c:1327
 kernel_init_freeable+0x3ed/0x580 init/main.c:1564
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880273b0100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880273b0180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880273b0200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff8880273b0280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880273b0300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/27 09:38 linux-6.6.y 0a40c6fbd105 2b01f00e .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/02/09 03:58 linux-6.6.y c56aaf1a85ae 4c131dc4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/05/27 00:47 linux-6.6.y 0a40c6fbd105 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/05/27 00:47 linux-6.6.y 0a40c6fbd105 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
* Struck through repros no longer work on HEAD.