[v6.6] KASAN: slab-use-after-free Read in dvb_frontend_release

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c56aaf1a85ae Linux 6.6.123
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1527865a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a950bf7c0bff9f9
dashboard link: https://syzkaller.appspot.com/bug?extid=c7c57465f74219389dc6
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=143deb22580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0c1480594070/disk-c56aaf1a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/118e64c14227/vmlinux-c56aaf1a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/320a7e9bfff1/bzImage-c56aaf1a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c7c574...@syzkaller.appspotmail.com

==================================================================
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 ffff888027100e3c by task syz.3.85/6227

CPU: 0 PID: 6227 Comm: syz.3.85 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
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+0x61/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f7b6f79aeb9
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:00007ffdd75ce068 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f7b6fa17da0 RCX: 00007f7b6f79aeb9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f7b6fa17da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007f7b6fa17cb0 R11: 0000000000000246 R12: 0000000000020835
R13: 00007f7b6fa1609c R14: 000000000002073f R15: 00007ffdd75ce170
</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:436 [inline]
vidtv_bridge_probe+0x9ab/0xf80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:508
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+0x18c/0x330 drivers/base/dd.c:800
driver_probe_device+0x4f/0x420 drivers/base/dd.c:830
__driver_attach+0x44e/0x6e0 drivers/base/dd.c:1216
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:598
do_one_initcall+0x242/0x790 init/main.c:1250
do_initcall_level+0x137/0x1f0 init/main.c:1312
do_initcalls+0x69/0xd0 init/main.c:1328
kernel_init_freeable+0x3ed/0x580 init/main.c:1565
kernel_init+0x1d/0x1c0 init/main.c:1455
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 6227:
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
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
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+0x61/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888027100e00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 60 bytes inside of
freed 256-byte region [ffff888027100e00, ffff888027100f00)

The buggy address belongs to the physical page:
page:ffffea00009c4000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27100
head:ffffea00009c4000 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 13945279534, 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:4486
alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2120
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
usb_register_driver+0x206/0x3d0 drivers/usb/core/driver.c:1062
pvr_init+0x7b/0x130 drivers/media/usb/pvrusb2/pvrusb2-main.c:112
do_one_initcall+0x242/0x790 init/main.c:1250
do_initcall_level+0x137/0x1f0 init/main.c:1312
do_initcalls+0x69/0xd0 init/main.c:1328
page_owner free stack trace missing

Memory state around the buggy address:
ffff888027100d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888027100d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888027100e00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888027100e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888027100f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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