KASAN: slab-out-of-bounds Read in l2cap_sock_setsockopt (2)

Status: upstream: reported on 2026/07/24 11:54
Subsystems: bluetooth
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+b106284c2a0b7bc80cf9@syzkaller.appspotmail.com
Fix commit: Bluetooth: L2CAP: access chan->conn safely in get/setsockopt
Patched on: [ci-upstream-linux-next-kasan-gce-root], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 26d, last: 16d
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
a8474b40 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ❌ ❓ KASAN: slab-out-of-bounds Read in l2cap_sock_setsockopt (2) 2026/07/21 00:42 2026/07/21 00:42 2026/07/21 01:37 de6a700d
▶ ▼ Discussions (3)
Title Replies (including bot) Last reply
[PATCH] Bluetooth: L2CAP: access chan->conn safely in get/setsockopt 2 (2) 2026/08/11 20:10
[syzbot] Monthly bluetooth report (Aug 2026) 0 (1) 2026/08/04 12:32
[syzbot] [bluetooth?] KASAN: slab-out-of-bounds Read in l2cap_sock_setsockopt (2) 0 (1) 2026/07/24 11:54
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 KASAN: slab-out-of-bounds Read in l2cap_sock_setsockopt origin:lts 17 syz, C error 6 4d04h 213d 0/2 upstream: reported C repro on 2026/01/14 12:28
upstream KASAN: slab-out-of-bounds Read in l2cap_sock_setsockopt bluetooth 17 syz, C 36 852d 862d 0/29 auto-obsoleted due to no activity on 2024/06/24 18:09

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in l2cap_sock_setsockopt+0x22c3/0x2330 net/bluetooth/l2cap_sock.c:1003
Read of size 1 at addr ffff88802803c362 by task syz.1.1719/10814

CPU: 1 UID: 0 PID: 10814 Comm: syz.1.1719 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 l2cap_sock_setsockopt+0x22c3/0x2330 net/bluetooth/l2cap_sock.c:1003
 do_sock_setsockopt+0xf3/0x1d0 net/socket.c:2368
 __sys_setsockopt+0x195/0x220 net/socket.c:2393
 __do_sys_setsockopt net/socket.c:2399 [inline]
 __se_sys_setsockopt net/socket.c:2396 [inline]
 __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2396
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbdccd9de99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fbdcaff6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007fbdcd025fa0 RCX: 00007fbdccd9de99
RDX: 0000000000000008 RSI: 0000000000000112 RDI: 0000000000000004
RBP: 00007fbdcce33eaf R08: 0000000000000004 R09: 0000000000000000
R10: 00002000000005c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbdcd026038 R14: 00007fbdcd025fa0 R15: 00007fffc6ab0ee8
 </TASK>

The buggy address belongs to the object at ffff88802803c340
 which belongs to the cache skbuff_small_head of size 704
The buggy address is located 34 bytes inside of
 allocated 704-byte region [ffff88802803c340, ffff88802803c600)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2803c
head: order:2 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 ffff88801cb40500 dead000000000122 0000000000000000
raw: 0000000000000000 0000000800130013 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801cb40500 dead000000000122 0000000000000000
head: 0000000000000000 0000000800130013 00000000f5000000 0000000000000000
head: 00fff00000000002 ffffffffffffff01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd2000(__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5813, tgid 5813 (kworker/u32:4), ts 280325981720, free_ts 280258613659
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0xf48/0x3530 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x299/0x2dc0 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab mm/slub.c:3408 [inline]
 new_slab+0xa2/0x650 mm/slub.c:3454
 refill_objects+0xe3/0x410 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x376/0x680 mm/slub.c:4703
 alloc_from_pcs mm/slub.c:4801 [inline]
 slab_alloc_node mm/slub.c:4933 [inline]
 kmem_cache_alloc_node_noprof+0x52c/0x6b0 mm/slub.c:5017
 kmalloc_reserve+0x148/0x350 net/core/skbuff.c:615
 __alloc_skb+0x185/0x710 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1384 [inline]
 alloc_uevent_skb+0x7d/0x210 lib/kobject_uevent.c:289
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast lib/kobject_uevent.c:410 [inline]
 kobject_uevent_env+0xd2d/0x18b0 lib/kobject_uevent.c:611
 device_del+0x605/0x9b0 drivers/base/core.c:3979
 device_unregister+0x1d/0xe0 drivers/base/core.c:4002
 mac80211_hwsim_del_radio drivers/net/wireless/virtual/mac80211_hwsim_main.c:6228 [inline]
 hwsim_exit_net+0x8c2/0x14f0 drivers/net/wireless/virtual/mac80211_hwsim_main.c:7207
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x2ee/0xab0 net/core/net_namespace.c:252
 cleanup_net+0x499/0x920 net/core/net_namespace.c:702
page last free pid 10776 tgid 10776 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x79f/0x1090 mm/page_alloc.c:2950
 hci_release_dev+0x4ef/0x630 net/bluetooth/hci_core.c:2739
 bt_host_release+0x6b/0xb0 net/bluetooth/hci_sysfs.c:87
 device_release+0xd2/0x270 drivers/base/core.c:2636
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device+0x1f/0x30 drivers/base/core.c:3880
 vhci_release+0x185/0x230 drivers/bluetooth/hci_vhci.c:701
 __fput+0x3ff/0xb50 fs/file_table.c:512
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2ae0 kernel/exit.c:1009
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1152
 __do_sys_exit_group kernel/exit.c:1163 [inline]
 __se_sys_exit_group kernel/exit.c:1161 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1161
 x64_sys_call+0x102c/0x1530 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88802803c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802803c280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802803c300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                       ^
 ffff88802803c380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802803c400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/19 23:34 upstream c6859eed755d 72524a66 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in l2cap_sock_setsockopt
2026/07/30 09:50 upstream 11028ab62899 abc81b93 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: use-after-free Read in l2cap_sock_setsockopt
* Struck through repros no longer work on HEAD.