[syzbot] [bluetooth?] KASAN: slab-use-after-free Read in skb_pull (2)

[syzbot <syzbot+da2717d5c64bf7975268@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    0787c45ea08a Add linux-next specific files for 20260429
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12e219ba580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dc6dd31c8eef55aa
dashboard link: https://syzkaller.appspot.com/bug?extid=da2717d5c64bf7975268
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/2eccbc923d17/disk-0787c45e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/68b90b45c92d/vmlinux-0787c45e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a5b9de0f776c/bzImage-0787c45e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+da2717d5c64bf7975268@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in skb_pull_inline include/linux/skbuff.h:2853 [inline]
BUG: KASAN: slab-use-after-free in skb_pull+0x133/0x1d0 net/core/skbuff.c:2664
Read of size 4 at addr ffff888040ca5e30 by task kworker/0:8/5871

CPU: 0 UID: 0 PID: 5871 Comm: kworker/0:8 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Comput[  699.645251][ T5871] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events hci_uart_write_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 skb_pull_inline include/linux/skbuff.h:2853 [inline]
 skb_pull+0x133/0x1d0 net/core/skbuff.c:2664
 hci_uart_write_work+0x44d/0x720 drivers/bluetooth/hci_ldisc.c:168
 process_one_work+0x9a3/0x1710 kernel/workqueue.c:3312
 process_scheduled_works kernel/workqueue.c:3403 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3489
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 9:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4577 [inline]
 slab_alloc_node mm/slub.c:4906 [inline]
 kmem_cache_alloc_node_noprof+0x22a/0x6e0 mm/slub.c:4958
 __alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
 alloc_skb include/linux/skbuff.h:1383 [inline]
 h5_prepare_pkt+0x1b3/0xc40 drivers/bluetooth/hci_h5.c:728
 h5_dequeue+0x1ba/0x840 drivers/bluetooth/hci_h5.c:797
 hci_uart_dequeue drivers/bluetooth/hci_ldisc.c:107 [inline]
 hci_uart_write_work+0x29b/0x720 drivers/bluetooth/hci_ldisc.c:161
 process_one_work+0x9a3/0x1710 kernel/workqueue.c:3312
 process_scheduled_works kernel/workqueue.c:3403 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3489
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 15008:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2700 [inline]
 slab_free mm/slub.c:6258 [inline]
 kmem_cache_free+0x187/0x6c0 mm/slub.c:6385
 kfree_skb_reason include/linux/skbuff.h:1322 [inline]
 kfree_skb include/linux/skbuff.h:1331 [inline]
 hci_uart_flush+0x9d/0x360 drivers/bluetooth/hci_ldisc.c:235
 hci_uart_close drivers/bluetooth/hci_ldisc.c:268 [inline]
 hci_uart_tty_close+0x99/0x2d0 drivers/bluetooth/hci_ldisc.c:545
 tty_ldisc_kill drivers/tty/tty_ldisc.c:613 [inline]
 tty_ldisc_hangup+0x444/0x630 drivers/tty/tty_ldisc.c:729
 __tty_hangup+0x3eb/0x660 drivers/tty/tty_io.c:621
 tty_vhangup drivers/tty/tty_io.c:691 [inline]
 tty_ioctl+0x75d/0xde0 drivers/tty/tty_io.c:2732
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888040ca5dc0
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 112 bytes inside of
 freed 240-byte region [ffff888040ca5dc0, ffff888040ca5eb0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x40ca5
memcg:ffff888040e64101
flags: 0x80000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000000 ffff88801dac5a00 dead000000000100 dead000000000122
raw: 0000000000000000 00000008000c000c 00000000f5000000 ffff888040e64101
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1182, tgid 1182 (kworker/u8:10), ts 217707286874, free_ts 217702375992
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x27d6/0x2850 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5249
 alloc_slab_page mm/slub.c:3289 [inline]
 allocate_slab+0x74/0x5e0 mm/slub.c:3404
 new_slab mm/slub.c:3447 [inline]
 refill_objects+0x33c/0x3d0 mm/slub.c:7263
 refill_sheaf mm/slub.c:2827 [inline]
 __pcs_replace_empty_main+0x373/0x720 mm/slub.c:4659
 alloc_from_pcs mm/slub.c:4757 [inline]
 slab_alloc_node mm/slub.c:4891 [inline]
 kmem_cache_alloc_node_noprof+0x4f4/0x6e0 mm/slub.c:4958
 __alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:819 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
 nsim_dev_trap_report_work+0x29f/0xbd0 drivers/net/netdevsim/dev.c:922
 process_one_work+0x9a3/0x1710 kernel/workqueue.c:3312
 process_scheduled_works kernel/workqueue.c:3403 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3489
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 29 tgid 29 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1397 [inline]
 __free_frozen_pages+0x1075/0x11b0 mm/page_alloc.c:2938
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core kernel/rcu/tree.c:2869 [inline]
 rcu_cpu_kthread+0x99e/0x1470 kernel/rcu/tree.c:2957
 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff888040ca5d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff888040ca5d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff888040ca5e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888040ca5e80: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
 ffff888040ca5f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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