syzbot


KASAN: use-after-free Read in hci_uart_write_work (2)

Status: premoderation: reported on 2026/02/05 14:27
Reported-by: syzbot+205215db8d00f2b56c41@syzkaller.appspotmail.com
First crash: 41d, last: 41d
Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in hci_uart_write_work 19 1 55d 55d 0/3 upstream: reported on 2026/01/23 06:14
android-5-15 KASAN: use-after-free Read in hci_uart_write_work 19 1 174d 174d 0/2 auto-obsoleted due to no activity on 2025/12/25 00:53
android-6-1 KASAN: use-after-free Read in hci_uart_write_work 19 7 172d 192d 0/2 auto-obsoleted due to no activity on 2025/12/27 01:39
android-5-10 KASAN: use-after-free Read in hci_uart_write_work 19 2 140d 153d 0/2 auto-obsoleted due to no activity on 2026/01/28 02:36
android-6-12 KASAN: slab-use-after-free Read in hci_uart_write_work 19 1 189d 189d 0/1 auto-obsoleted due to no activity on 2025/12/10 04:09
upstream KASAN: slab-use-after-free Read in hci_uart_write_work bluetooth 19 syz error error 78 32d 247d 0/29 upstream: reported syz repro on 2025/07/14 17:09

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in hci_uart_write_work+0x3df/0x6e0 drivers/bluetooth/hci_ldisc.c:165
Read of size 8 at addr ffff88810f776ae0 by task kworker/1:0/20

CPU: 1 PID: 20 Comm: kworker/1:0 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events hci_uart_write_work
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
 hci_uart_write_work+0x3df/0x6e0 drivers/bluetooth/hci_ldisc.c:165
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13c0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Allocated by task 662:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 __kasan_slab_alloc+0xbd/0xf0 mm/kasan/common.c:463
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x162/0x2d0 mm/slub.c:2965
 kmem_cache_alloc_node include/linux/slab.h:426 [inline]
 __alloc_skb+0x9e/0x520 net/core/skbuff.c:200
 alloc_skb include/linux/skbuff.h:1126 [inline]
 bt_skb_alloc include/net/bluetooth/bluetooth.h:391 [inline]
 hci_prepare_cmd net/bluetooth/hci_request.c:298 [inline]
 hci_req_add_ev+0x98/0x3c0 net/bluetooth/hci_request.c:332
 hci_req_add+0x30/0x40 net/bluetooth/hci_request.c:351
 bredr_init net/bluetooth/hci_core.c:202 [inline]
 hci_init1_req+0x13c/0x280 net/bluetooth/hci_core.c:258
 __hci_req_sync+0x14b/0x7f0 net/bluetooth/hci_request.c:207
 __hci_init+0x2f/0x3b0 net/bluetooth/hci_core.c:907
 hci_dev_do_open+0xa61/0x1150 net/bluetooth/hci_core.c:1573
 hci_power_on+0x1b5/0x5b0 net/bluetooth/hci_core.c:2253
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13c0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Freed by task 989:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3224
 kfree_skbmem+0x10c/0x180 net/core/skbuff.c:-1
 __kfree_skb net/core/skbuff.c:695 [inline]
 kfree_skb+0xc1/0x2f0 net/core/skbuff.c:713
 hci_uart_flush+0x95/0x320 drivers/bluetooth/hci_ldisc.c:235
 hci_uart_close drivers/bluetooth/hci_ldisc.c:268 [inline]
 hci_uart_tty_close+0x7a/0x220 drivers/bluetooth/hci_ldisc.c:539
 tty_ldisc_close drivers/tty/tty_ldisc.c:489 [inline]
 tty_ldisc_kill+0x101/0x220 drivers/tty/tty_ldisc.c:637
 tty_ldisc_hangup+0x3df/0x4f0 drivers/tty/tty_ldisc.c:756
 __tty_hangup+0x60d/0x870 drivers/tty/tty_io.c:625
 tty_vhangup drivers/tty/tty_io.c:698 [inline]
 tty_ioctl+0x4d1/0xc60 drivers/tty/tty_io.c:2689
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:739
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:739
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88810f776a00
 which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 224 bytes inside of
 248-byte region [ffff88810f776a00, ffff88810f776af8)
The buggy address belongs to the page:
page:ffffea00043ddd80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10f776
flags: 0x4000000000000200(slab)
raw: 4000000000000200 dead000000000100 dead000000000122 ffff888107d92780
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 103, ts 5390859150, free_ts 5390535512
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x223b/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x290/0x620 mm/page_alloc.c:5370
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x1ac/0x2d0 mm/slub.c:2965
 kmem_cache_alloc_node include/linux/slab.h:426 [inline]
 __alloc_skb+0x9e/0x520 net/core/skbuff.c:200
 alloc_skb include/linux/skbuff.h:1126 [inline]
 netlink_alloc_large_skb net/netlink/af_netlink.c:1178 [inline]
 netlink_sendmsg+0x605/0xb50 net/netlink/af_netlink.c:1889
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 ____sys_sendmsg+0x5b7/0x8f0 net/socket.c:2376
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2430
 __sys_sendmsg net/socket.c:2459 [inline]
 __do_sys_sendmsg net/socket.c:2468 [inline]
 __se_sys_sendmsg net/socket.c:2466 [inline]
 __x64_sys_sendmsg+0x1f9/0x2c0 net/socket.c:2466
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 free_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336
 free_unref_page mm/page_alloc.c:3391 [inline]
 free_the_page mm/page_alloc.c:5429 [inline]
 __free_pages+0x146/0x3b0 mm/page_alloc.c:5440
 free_pages+0x82/0x90 mm/page_alloc.c:5451
 selinux_genfs_get_sid+0x20b/0x250 security/selinux/hooks.c:1332
 inode_doinit_with_dentry+0x879/0xd70 security/selinux/hooks.c:1529
 selinux_d_instantiate+0x27/0x40 security/selinux/hooks.c:6395
 security_d_instantiate+0x9e/0xf0 security/security.c:1980
 d_splice_alias+0x6d/0x390 fs/dcache.c:3038
 kernfs_iop_lookup+0x2c5/0x310 fs/kernfs/dir.c:1178
 lookup_open fs/namei.c:3234 [inline]
 open_last_lookups fs/namei.c:3325 [inline]
 path_openat+0x1140/0x31c0 fs/namei.c:3514
 do_filp_open+0x1e2/0x410 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
 do_sys_open fs/open.c:1235 [inline]
 __do_sys_openat fs/open.c:1251 [inline]
 __se_sys_openat fs/open.c:1246 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1246
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff88810f776980: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
 ffff88810f776a00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810f776a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
                                                       ^
 ffff88810f776b00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff88810f776b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
usb 4-1: reset full-speed USB device number 4 using dummy_hcd
usb 4-1: device descriptor read/64, error -32
usb 4-1: device descriptor read/64, error -32
usb 4-1: reset full-speed USB device number 4 using dummy_hcd
usb 4-1: device descriptor read/64, error -32
usb 4-1: device descriptor read/64, error -32
usb 4-1: reset full-speed USB device number 4 using dummy_hcd
usb 4-1: device descriptor read/8, error -32
usb 4-1: device descriptor read/8, error -32
usb 4-1: reset full-speed USB device number 4 using dummy_hcd
usb 4-1: device descriptor read/8, error -32
usb 4-1: device descriptor read/8, error -32

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/05 14:26 android13-5.10-lts 58c592510fcd 4936e85c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in hci_uart_write_work
* Struck through repros no longer work on HEAD.