KASAN: slab-use-after-free Read in release_sock

Status: upstream: reported C repro on 2025/07/18 09:37
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+be6b1fdfeae512726b4e@syzkaller.appspotmail.com
First crash: 384d, last: 214d
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: KASAN: slab-use-after-free Read in lock_sock_nested (log)
Repro: C syz .config
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[PATCH net v2] net: kcm: Fix race condition in kcm_unattach() 2 (2) 2025/08/14 01:30
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2025/09/06 linux-6.6.y (ToT) 355bd0b51d2f C [report] KASAN: slab-use-after-free Read in __lock_sock
2025/07/18 upstream (ToT) 6832a9317eee C [report] KASAN: slab-use-after-free Read in __lock_sock
2025/09/06 upstream (ToT) d1d10cea0895 C Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in release_sock (2) bluetooth 19 1 350d 344d 29/29 fixed on 2025/10/29 21:02
upstream KASAN: slab-use-after-free Read in release_sock bluetooth 19 1 1021d 1016d 0/29 auto-obsoleted due to no activity on 2024/01/28 22:15
upstream general protection fault in release_sock bluetooth 2 1 1799d 1799d 0/29 closed as invalid on 2021/10/01 22:57
linux-6.1 KASAN: use-after-free Read in release_sock origin:upstream missing-backport 19 syz, C inconclusive 1 329d 368d 0/3 upstream: reported C repro on 2025/08/02 23:19
▶ ▼ Fix bisection attempts (10)
Created Duration User Patch Repo Result
2026/07/09 11:47 4h27m fix candidate upstream OK (0) job log
2026/05/25 00:25 19m fix candidate upstream error job log
2026/03/25 12:50 2m fix candidate upstream error job log
2026/02/23 08:32 1m fix candidate upstream error job log
2026/01/24 03:37 1m fix candidate upstream error job log
2026/01/04 16:45 3h13m bisect fix linux-6.6.y OK (0) job log log
2025/12/02 17:40 3h01m bisect fix linux-6.6.y OK (0) job log log
2025/11/01 07:29 2h12m bisect fix linux-6.6.y OK (0) job log log
2025/09/22 09:48 3h36m bisect fix linux-6.6.y OK (0) job log log
2025/08/17 13:47 2h22m bisect fix linux-6.6.y OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in __lock_acquire+0xff/0x7c80 kernel/locking/lockdep.c:5005
Read of size 8 at addr ffff88807d0e9db0 by task kworker/u4:3/48

CPU: 1 PID: 48 Comm: kworker/u4:3 Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: kkcmd kcm_tx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x200 mm/kasan/report.c:466
 kasan_report+0x117/0x150 mm/kasan/report.c:579
 __lock_acquire+0xff/0x7c80 kernel/locking/lockdep.c:5005
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 release_sock+0x2f/0x1c0 net/core/sock.c:3523
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Allocated by task 6383:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
 sk_prot_alloc+0x57/0x210 net/core/sock.c:2088
 sk_alloc+0x3a/0x360 net/core/sock.c:2147
 kcm_clone net/kcm/kcmsock.c:1518 [inline]
 kcm_ioctl+0x215/0xff0 net/kcm/kcmsock.c:1563
 sock_do_ioctl+0xd7/0x2f0 net/socket.c:1222
 sock_ioctl+0x623/0x7a0 net/socket.c:1341
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 6384:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1806 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1832
 slab_free mm/slub.c:3816 [inline]
 kmem_cache_free+0xf8/0x280 mm/slub.c:3838
 sk_prot_free net/core/sock.c:2128 [inline]
 __sk_destruct+0x485/0x620 net/core/sock.c:2222
 kcm_release+0x524/0x5b0 net/kcm/kcmsock.c:1738
 __sock_release net/socket.c:659 [inline]
 sock_close+0xbd/0x230 net/socket.c:1421
 __fput+0x234/0x970 fs/file_table.c:384
 __do_sys_close fs/open.c:1571 [inline]
 __se_sys_close+0x15f/0x220 fs/open.c:1556
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 insert_work+0x3d/0x310 kernel/workqueue.c:1651
 __queue_work+0xc39/0x1020 kernel/workqueue.c:1800
 queue_work_on+0x121/0x1e0 kernel/workqueue.c:1835
 queue_work include/linux/workqueue.h:562 [inline]
 kcm_unattach+0x861/0xe80 net/kcm/kcmsock.c:1427
 kcm_unattach_ioctl net/kcm/kcmsock.c:1484 [inline]
 kcm_ioctl+0x791/0xff0 net/kcm/kcmsock.c:1551
 sock_do_ioctl+0xd7/0x2f0 net/socket.c:1222
 sock_ioctl+0x623/0x7a0 net/socket.c:1341
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 insert_work+0x3d/0x310 kernel/workqueue.c:1651
 __queue_work+0xc39/0x1020 kernel/workqueue.c:1800
 queue_work_on+0x121/0x1e0 kernel/workqueue.c:1835
 kcm_attach net/kcm/kcmsock.c:1307 [inline]
 kcm_attach_ioctl net/kcm/kcmsock.c:1335 [inline]
 kcm_ioctl+0xe4f/0xff0 net/kcm/kcmsock.c:1541
 sock_do_ioctl+0xd7/0x2f0 net/socket.c:1222
 sock_ioctl+0x623/0x7a0 net/socket.c:1341
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88807d0e9d00
 which belongs to the cache KCM of size 1720
The buggy address is located 176 bytes inside of
 freed 1720-byte region [ffff88807d0e9d00, ffff88807d0ea3b8)

The buggy address belongs to the physical page:
page:ffffea0001f43a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7d0e8
head:ffffea0001f43a00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888024196201
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff88802c39d280 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080110011 00000001ffffffff ffff888024196201
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 6370, tgid 6369 (syz.0.119), ts 172058472506, free_ts 172056728285
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 alloc_slab_page+0x5d/0x170 mm/slub.c:1876
 allocate_slab mm/slub.c:2023 [inline]
 new_slab+0x87/0x2e0 mm/slub.c:2076
 ___slab_alloc+0xc6d/0x12f0 mm/slub.c:3230
 __slab_alloc mm/slub.c:3329 [inline]
 __slab_alloc_node mm/slub.c:3382 [inline]
 slab_alloc_node mm/slub.c:3475 [inline]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x1b7/0x2e0 mm/slub.c:3509
 sk_prot_alloc+0x57/0x210 net/core/sock.c:2088
 sk_alloc+0x3a/0x360 net/core/sock.c:2147
 kcm_create+0x100/0x570 net/kcm/kcmsock.c:1808
 __sock_create+0x4a6/0x940 net/socket.c:1571
 sock_create net/socket.c:1627 [inline]
 __sys_socket_create net/socket.c:1664 [inline]
 __sys_socket+0xd7/0x1a0 net/socket.c:1715
 __do_sys_socket net/socket.c:1729 [inline]
 __se_sys_socket net/socket.c:1727 [inline]
 __x64_sys_socket+0x7a/0x90 net/socket.c:1727
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2122 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2662
 put_cpu_partial+0x17c/0x250 mm/slub.c:2738
 __slab_free+0x31d/0x410 mm/slub.c:3686
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
 ptlock_alloc mm/memory.c:6155 [inline]
 ptlock_init include/linux/mm.h:2898 [inline]
 pmd_ptlock_init include/linux/mm.h:2998 [inline]
 pagetable_pmd_ctor include/linux/mm.h:3036 [inline]
 pmd_alloc_one include/asm-generic/pgalloc.h:137 [inline]
 __pmd_alloc+0x116/0x880 mm/memory.c:5577
 pmd_alloc include/linux/mm.h:2797 [inline]
 __handle_mm_fault mm/memory.c:5127 [inline]
 handle_mm_fault+0xb3d/0x4920 mm/memory.c:5331
 do_user_addr_fault+0xad0/0x12e0 arch/x86/mm/fault.c:1324
 handle_page_fault arch/x86/mm/fault.c:1465 [inline]
 exc_page_fault+0x67/0x110 arch/x86/mm/fault.c:1521
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608

Memory state around the buggy address:
 ffff88807d0e9c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807d0e9d00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807d0e9d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff88807d0e9e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807d0e9e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/18 09:36 linux-6.6.y d96eb99e2f0e 88248e14 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf KASAN: slab-use-after-free Read in release_sock
* Struck through repros no longer work on HEAD.