[moderation] [media?] KASAN: slab-use-after-free Write in dvb_device_put

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d4b779985a6c Merge tag 'for-6.17/dm-fixes' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12bd2e42580000
kernel config: https://syzkaller.appspot.com/x/.config?x=595e5938a1dd5b4e
dashboard link: https://syzkaller.appspot.com/bug?extid=65b718c44ea759358da9
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
CC: [linux-...@vger.kernel.org linux...@vger.kernel.org mch...@kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9a84e163c589/disk-d4b77998.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/050f34576399/vmlinux-d4b77998.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7a561c0f3881/bzImage-d4b77998.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+65b718...@syzkaller.appspotmail.com

R13: 00007fdf3abd6038 R14: 00007fdf3abd5fa0 R15: 00007ffc24915c58
</TASK>
i2c i2c-0: dvb_frontend_start: failed to start kthread (-12)
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
BUG: KASAN: slab-use-after-free in __refcount_sub_and_test include/linux/refcount.h:389 [inline]
BUG: KASAN: slab-use-after-free in __refcount_dec_and_test include/linux/refcount.h:432 [inline]
BUG: KASAN: slab-use-after-free in refcount_dec_and_test include/linux/refcount.h:450 [inline]
BUG: KASAN: slab-use-after-free in kref_put include/linux/kref.h:64 [inline]
BUG: KASAN: slab-use-after-free in dvb_device_put.part.0+0x22/0x90 drivers/media/dvb-core/dvbdev.c:632
Write of size 4 at addr ffff88802aae1610 by task syz.2.3292/14587

CPU: 1 UID: 0 PID: 14587 Comm: syz.2.3292 Tainted: G U syzkaller #0 PREEMPT(full)
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcd/0x630 mm/kasan/report.c:482
kasan_report+0xe0/0x110 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
__refcount_sub_and_test include/linux/refcount.h:389 [inline]
__refcount_dec_and_test include/linux/refcount.h:432 [inline]
refcount_dec_and_test include/linux/refcount.h:450 [inline]
kref_put include/linux/kref.h:64 [inline]
dvb_device_put.part.0+0x22/0x90 drivers/media/dvb-core/dvbdev.c:632
dvb_device_put drivers/media/dvb-core/dvbdev.c:631 [inline]
dvb_device_open+0x2a4/0x3b0 drivers/media/dvb-core/dvbdev.c:113
chrdev_open+0x234/0x6a0 fs/char_dev.c:414
do_dentry_open+0x982/0x1530 fs/open.c:965
vfs_open+0x82/0x3f0 fs/open.c:1095
do_open fs/namei.c:3887 [inline]
path_openat+0x1de4/0x2cb0 fs/namei.c:4046
do_filp_open+0x20b/0x470 fs/namei.c:4073
do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
do_sys_open fs/open.c:1450 [inline]
__do_sys_openat fs/open.c:1466 [inline]
__se_sys_openat fs/open.c:1461 [inline]
__x64_sys_openat+0x174/0x210 fs/open.c:1461
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdf3a98eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdf3b8e0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fdf3abd5fa0 RCX: 00007fdf3a98eba9
RDX: 0000000000000001 RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007fdf3aa11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdf3abd6038 R14: 00007fdf3abd5fa0 R15: 00007ffc24915c58
</TASK>

Allocated by task 1:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405
kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]
dvb_register_device+0x1e4/0x2370 drivers/media/dvb-core/dvbdev.c:475
dvb_register_frontend+0x5a6/0x880 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+0x459/0xa90 drivers/media/test-drivers/vidtv/vidtv_bridge.c:508
platform_probe+0x103/0x1d0 drivers/base/platform.c:1405
call_driver_probe drivers/base/dd.c:581 [inline]
really_probe+0x241/0xa90 drivers/base/dd.c:659
__driver_probe_device+0x1de/0x440 drivers/base/dd.c:801
driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:831
__driver_attach+0x283/0x580 drivers/base/dd.c:1217
bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:370
bus_add_driver+0x2e9/0x690 drivers/base/bus.c:678
driver_register+0x15c/0x4b0 drivers/base/driver.c:249
vidtv_bridge_init+0x45/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:598
do_one_initcall+0x120/0x6e0 init/main.c:1269
do_initcall_level init/main.c:1331 [inline]
do_initcalls init/main.c:1347 [inline]
do_basic_setup init/main.c:1366 [inline]
kernel_init_freeable+0x5c2/0x910 init/main.c:1579
kernel_init+0x1c/0x2b0 init/main.c:1469
ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 14593:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:243 [inline]
__kasan_slab_free+0x60/0x70 mm/kasan/common.c:275
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2422 [inline]
slab_free mm/slub.c:4695 [inline]
kfree+0x2b4/0x4d0 mm/slub.c:4894
dvb_free_device drivers/media/dvb-core/dvbdev.c:619 [inline]
kref_put include/linux/kref.h:65 [inline]
dvb_device_put.part.0+0x60/0x90 drivers/media/dvb-core/dvbdev.c:632
dvb_device_put drivers/media/dvb-core/dvbdev.c:631 [inline]
dvb_device_open+0x2a4/0x3b0 drivers/media/dvb-core/dvbdev.c:113
chrdev_open+0x234/0x6a0 fs/char_dev.c:414
do_dentry_open+0x982/0x1530 fs/open.c:965
vfs_open+0x82/0x3f0 fs/open.c:1095
do_open fs/namei.c:3887 [inline]
path_openat+0x1de4/0x2cb0 fs/namei.c:4046
do_filp_open+0x20b/0x470 fs/namei.c:4073
do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
do_sys_open fs/open.c:1450 [inline]
__do_sys_openat fs/open.c:1466 [inline]
__se_sys_openat fs/open.c:1461 [inline]
__x64_sys_openat+0x174/0x210 fs/open.c:1461
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802aae1600
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 16 bytes inside of
freed 256-byte region [ffff88802aae1600, ffff88802aae1700)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2aae0
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b841b40 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b841b40 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0000aab801 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
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 19212219133, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1851
prep_new_page mm/page_alloc.c:1859 [inline]
get_page_from_freelist+0x132b/0x38e0 mm/page_alloc.c:3858
__alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:5148
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:2492 [inline]
allocate_slab mm/slub.c:2660 [inline]
new_slab+0x247/0x330 mm/slub.c:2714
___slab_alloc+0xcf2/0x1750 mm/slub.c:3901
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3992
__slab_alloc_node mm/slub.c:4067 [inline]
slab_alloc_node mm/slub.c:4228 [inline]
__kmalloc_cache_noprof+0xfb/0x3e0 mm/slub.c:4402
kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]
bus_add_driver+0x92/0x690 drivers/base/bus.c:662
driver_register+0x15c/0x4b0 drivers/base/driver.c:249
usb_register_driver+0x216/0x4d0 drivers/usb/core/driver.c:1078
do_one_initcall+0x120/0x6e0 init/main.c:1269
do_initcall_level init/main.c:1331 [inline]
do_initcalls init/main.c:1347 [inline]
do_basic_setup init/main.c:1366 [inline]
kernel_init_freeable+0x5c2/0x910 init/main.c:1579
kernel_init+0x1c/0x2b0 init/main.c:1469
ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148
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:
ffff88802aae1500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802aae1580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802aae1600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802aae1680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802aae1700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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[Marco Elver]

#syz upstream

On Sun, 21 Sept 2025 at 22:35, syzbot

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