[v5.15] KASAN: use-after-free Read in dvb_frontend_release

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3330a8d33e08 Linux 5.15.201
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13461006580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=944142359d6049a49b15
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=12734952580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b65fe19af112/disk-3330a8d3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/351948519a0d/vmlinux-3330a8d3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a3b3f8477595/bzImage-3330a8d3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+944142...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in dvb_frontend_release+0x3fb/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2903
Read of size 4 at addr ffff88802776263c by task syz.3.31/4443

CPU: 1 PID: 4443 Comm: syz.3.31 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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+0x3fb/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2903
__fput+0x234/0x930 fs/file_table.c:311
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
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: 0033:0x7fae03834799
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:00007ffc1e0482d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fae03aafda0 RCX: 00007fae03834799
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fae03aafda0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007fae03aafcb0 R11: 0000000000000246 R12: 0000000000014c59
R13: 00007fae03aae09c R14: 0000000000014bf4 R15: 00007ffc1e0483e0
</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+0xb5/0xf0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
dvb_register_device+0x311/0x2170 drivers/media/dvb-core/dvbdev.c:488
dvb_register_frontend+0x645/0x920 drivers/media/dvb-core/dvb_frontend.c:3034
vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:436 [inline]
vidtv_bridge_probe+0x9a1/0xf70 drivers/media/test-drivers/vidtv/vidtv_bridge.c:508
platform_probe+0x137/0x1c0 drivers/base/platform.c:1391
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x284/0xc80 drivers/base/dd.c:595
__driver_probe_device+0x18c/0x330 drivers/base/dd.c:755
driver_probe_device+0x4f/0x420 drivers/base/dd.c:785
__driver_attach+0x46b/0x670 drivers/base/dd.c:1164
bus_for_each_dev+0x182/0x1f0 drivers/base/bus.c:303
bus_add_driver+0x30a/0x5a0 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:600
do_one_initcall+0x272/0x730 init/main.c:1316
do_initcall_level+0x137/0x1f0 init/main.c:1389
do_initcalls+0x4b/0x90 init/main.c:1405
kernel_init_freeable+0x3e9/0x570 init/main.c:1629
kernel_init+0x19/0x1b0 init/main.c:1520
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 4443:
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+0xea/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+0x234/0x930 fs/file_table.c:311
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
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 ffff888027762600
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 60 bytes inside of
256-byte region [ffff888027762600, ffff888027762700)
The buggy address belongs to the page:
page:ffffea00009dd880 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27762
head:ffffea00009dd880 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 2821, ts 15493559408, free_ts 0
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
__alloc_pages+0x1ee/0x480 mm/page_alloc.c:5487
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+0x80a/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+0x1a5/0x2a0 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+0x10b/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:
ffff888027762500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888027762580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888027762600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888027762680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888027762700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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