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KASAN: use-after-free Read in hci_uart_write_work

Status: premoderation: reported on 2025/10/16 23:25
Reported-by: syzbot+1b4ec1f804f3ed61be32@syzkaller.appspotmail.com
First crash: 4d07h, last: 4d07h
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 KASAN: use-after-free Read in hci_uart_write_work 19 1 25d 25d 0/2 premoderation: reported on 2025/09/26 00:52
android-6-1 KASAN: use-after-free Read in hci_uart_write_work 19 7 23d 42d 0/2 premoderation: reported on 2025/09/08 09:39
android-6-12 KASAN: slab-use-after-free Read in hci_uart_write_work 19 1 40d 40d 0/1 premoderation: reported on 2025/09/11 04:00
upstream KASAN: slab-use-after-free Read in hci_uart_write_work bluetooth 19 syz 7 4d03h 98d 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 ffff88810d331220 by task kworker/0:7/621

CPU: 0 PID: 621 Comm: kworker/0:7 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: events hci_uart_write_work
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 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/0x13b0 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 2212:
 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+0x165/0x2e0 mm/slub.c:2965
 kmem_cache_alloc_node include/linux/slab.h:423 [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+0x136/0x7b0 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/0x13b0 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 3468:
 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 ffff88810d331140
 which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 224 bytes inside of
 248-byte region [ffff88810d331140, ffff88810d331238)
The buggy address belongs to the page:
page:ffffea000434cc40 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88810d3313c0 pfn:0x10d331
flags: 0x4000000000000200(slab)
raw: 4000000000000200 ffffea0004b83780 0000000200000002 ffff888107d95980
raw: ffff88810d3313c0 00000000800c0005 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 0x112a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 2372, ts 122032616591, free_ts 121977270237
 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+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 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+0x1af/0x2e0 mm/slub.c:2965
 __build_skb+0x2d/0x310 net/core/skbuff.c:318
 build_skb+0x24/0x200 net/core/skbuff.c:334
 __tun_build_skb drivers/net/tun.c:1619 [inline]
 tun_build_skb drivers/net/tun.c:1704 [inline]
 tun_get_user+0x818/0x3090 drivers/net/tun.c:1832
 tun_chr_write_iter+0x1bf/0x270 drivers/net/tun.c:2059
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x725/0xd60 fs/read_write.c:605
 ksys_write+0x140/0x240 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 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+0x14b/0x380 mm/page_alloc.c:5440
 __vunmap+0x84d/0x9d0 mm/vmalloc.c:2307
 free_work+0x5a/0x80 mm/vmalloc.c:69
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Memory state around the buggy address:
 ffff88810d331100: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff88810d331180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810d331200: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
                               ^
 ffff88810d331280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810d331300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/16 23:24 android13-5.10-lts 2ece552169c2 19568248 .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.