[v5.15] KASAN: slab-out-of-bounds Write in try_module_get

[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=1067e8d6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=16d5985fa5c27b7d23f4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

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+16d598...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: slab-out-of-bounds in atomic_inc_not_zero include/linux/atomic/atomic-instrumented.h:577 [inline]
BUG: KASAN: slab-out-of-bounds in try_module_get+0x4f/0xf0 kernel/module.c:1076
Write of size 4 at addr ffff88802a0d27a0 by task syz.3.641/6963

CPU: 0 PID: 6963 Comm: syz.3.641 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
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_inc_not_zero include/linux/atomic/atomic-instrumented.h:577 [inline]
try_module_get+0x4f/0xf0 kernel/module.c:1076
dvb_device_open+0xf1/0x370 drivers/media/dvb-core/dvbdev.c:113
chrdev_open+0x5c5/0x6a0 fs/char_dev.c:414
do_dentry_open+0x7ff/0xf80 fs/open.c:826
do_open fs/namei.c:3616 [inline]
path_openat+0x26f5/0x2fa0 fs/namei.c:3750
do_filp_open+0x1e2/0x410 fs/namei.c:3777
do_sys_openat2+0x150/0x4b0 fs/open.c:1255
do_sys_open fs/open.c:1271 [inline]
__do_sys_openat fs/open.c:1287 [inline]
__se_sys_openat fs/open.c:1282 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1282
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fcdcd094fce
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007fcdcb30cb28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fcdcb30d6c0 RCX: 00007fcdcd094fce
RDX: 0000000000000e82 RSI: 00007fcdcb30cc00 RDI: ffffffffffffff9c
RBP: 00007fcdcb30cc00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: cccccccccccccccd
R13: 00007fcdcd34e128 R14: 00007fcdcd34e090 R15: 00007ffd11537198
</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_dmxdev_init+0x2c5/0x420 drivers/media/dvb-core/dmxdev.c:1440
vidtv_bridge_dmxdev_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:343 [inline]
vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:445 [inline]
vidtv_bridge_probe+0xb56/0xf70 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

The buggy address belongs to the object at ffff88802a0d2600
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 160 bytes to the right of
256-byte region [ffff88802a0d2600, ffff88802a0d2700)
The buggy address belongs to the page:
page:ffffea0000a83480 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88802a0d2000 pfn:0x2a0d2
head:ffffea0000a83480 order:1 compound_mapcount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00008ea888 ffffea0000ad8b88 ffff888016c41b40
raw: ffff88802a0d2000 000000000010000e 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 2837, ts 13623096491, 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:
ffff88802a0d2680: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
ffff88802a0d2700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802a0d2780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88802a0d2800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88802a0d2880: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
==================================================================


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