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

Status: upstream: reported C repro on 2026/08/10 00:23
Subsystems: afs net
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+c876adfab6362679008c@syzkaller.appspotmail.com
First crash: 5d23h, last: 1h06m
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
148b52c4 patching 🏃 KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers 2026/08/10 14:12 2026/08/10 14:12 039457bd
6a78f5da assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers 2026/08/09 11:50 2026/08/09 11:50 2026/08/09 13:25 5d63f80b
f31751cb repro-c Reproduced: ✅
❓ KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers 2026/08/08 08:32 2026/08/08 15:32 2026/08/08 16:23 5d63f80b
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] [afs?] KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers 0 (2) 2026/08/10 13:22
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/08/10 07:30 33m nogikh@google.com upstream report log

Sample crash report:
rxrpc: Leaked peer 4dfc {1} 127.0.0.1:8051
rxrpc: Leaked peer 5009 {1} 127.0.0.1:8167
rxrpc: Leaked peer 5726 {1} 127.0.0.1:8581
rxrpc: Leaked peer 5523 {0} 127.0.0.1:8374
==================================================================
BUG: KASAN: slab-use-after-free in rxrpc_destroy_all_peers+0x1ce/0x1d0 net/rxrpc/peer_object.c:461
Read of size 8 at addr ffff888054f70c20 by task kworker/u8:3/48

CPU: 0 UID: 0 PID: 48 Comm: kworker/u8:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: netns cleanup_net
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
 rxrpc_destroy_all_peers+0x1ce/0x1d0 net/rxrpc/peer_object.c:461
 rxrpc_exit_net+0x83/0xc0 net/rxrpc/net_ns.c:114
 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
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6240:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x2e5/0x6c0 mm/slub.c:5489
 _kmalloc_noprof include/linux/slab.h:988 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 rxrpc_alloc_peer+0xa7/0x400 net/rxrpc/peer_object.c:229
 rxrpc_create_peer net/rxrpc/peer_object.c:293 [inline]
 rxrpc_lookup_peer+0x168/0x680 net/rxrpc/peer_object.c:354
 rxrpc_kernel_lookup_peer+0xa8/0xe0 net/rxrpc/af_rxrpc.c:285
 afs_merge_fs_addr4+0x1cd/0x4c0 fs/afs/addr_list.c:300
 afs_parse_text_addrs+0x655/0xa10 fs/afs/addr_list.c:220
 afs_alloc_cell fs/afs/cell.c:181 [inline]
 afs_lookup_cell+0xbb6/0x1940 fs/afs/cell.c:273
 afs_proc_cells_write+0x2a3/0x3a0 fs/afs/proc.c:125
 proc_simple_write+0x10e/0x1a0 fs/proc/generic.c:843
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x240/0x330 fs/proc/inode.c:342
 vfs_write+0x2aa/0x1050 fs/read_write.c:685
 ksys_write+0x12a/0x250 fs/read_write.c:739
 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

Freed by task 16:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2677 [inline]
 __rcu_free_sheaf_prepare+0x5d/0x2f0 mm/slub.c:2928
 rcu_free_sheaf+0x1a/0xe0 mm/slub.c:5978
 rcu_do_batch kernel/rcu/tree.c:2645 [inline]
 rcu_core+0x5a2/0x10d0 kernel/rcu/tree.c:2897
 handle_softirqs+0x1ea/0x9b0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x162/0x210 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_call_function_single arch/x86/kernel/smp.c:267 [inline]
 sysvec_call_function_single+0xa3/0xc0 arch/x86/kernel/smp.c:267
 asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:681

The buggy address belongs to the object at ffff888054f70c00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 32 bytes inside of
 freed 512-byte region [ffff888054f70c00, ffff888054f70e00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x54f70
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 ffff88813fe21c80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe21c80 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6240, tgid 6240 (syz-executor166), ts 101070694469, free_ts 79760049897
 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:3266 [inline]
 allocate_slab mm/slub.c:3380 [inline]
 new_slab+0xa2/0x640 mm/slub.c:3426
 refill_objects+0xe3/0x410 mm/slub.c:7310
 refill_sheaf mm/slub.c:2804 [inline]
 __pcs_replace_empty_main+0x376/0x680 mm/slub.c:4675
 alloc_from_pcs mm/slub.c:4773 [inline]
 slab_alloc_node mm/slub.c:4905 [inline]
 __kmalloc_cache_noprof+0x479/0x6c0 mm/slub.c:5485
 _kmalloc_noprof include/linux/slab.h:988 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 rxrpc_alloc_peer+0xa7/0x400 net/rxrpc/peer_object.c:229
 rxrpc_create_peer net/rxrpc/peer_object.c:293 [inline]
 rxrpc_lookup_peer+0x168/0x680 net/rxrpc/peer_object.c:354
 rxrpc_kernel_lookup_peer+0xa8/0xe0 net/rxrpc/af_rxrpc.c:285
 afs_merge_fs_addr4+0x1cd/0x4c0 fs/afs/addr_list.c:300
 afs_parse_text_addrs+0x655/0xa10 fs/afs/addr_list.c:220
 afs_alloc_cell fs/afs/cell.c:181 [inline]
 afs_lookup_cell+0xbb6/0x1940 fs/afs/cell.c:273
 afs_proc_cells_write+0x2a3/0x3a0 fs/afs/proc.c:125
 proc_simple_write+0x10e/0x1a0 fs/proc/generic.c:843
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x240/0x330 fs/proc/inode.c:342
page last free pid 5674 tgid 5674 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_pages_prepare+0x586/0xd80 mm/page_alloc.c:1451
 __free_contig_range_common+0x14f/0x250 mm/page_alloc.c:6897
 __free_contig_range mm/page_alloc.c:6942 [inline]
 free_pages_bulk+0x12a/0x200 mm/page_alloc.c:5257
 vm_area_free_pages+0xad/0x2b0 mm/vmalloc.c:3461
 vfree mm/vmalloc.c:3510 [inline]
 vfree+0x107/0x750 mm/vmalloc.c:3484
 kcov_put kernel/kcov.c:447 [inline]
 kcov_put kernel/kcov.c:443 [inline]
 kcov_close+0x34/0x60 kernel/kcov.c:554
 __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
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3046
 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x139/0x6f0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888054f70b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888054f70b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888054f70c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888054f70c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888054f70d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/10 13:21 upstream db2ddb871435 5d63f80b .config console log report C ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
2026/08/09 13:28 upstream 06cf61899d64 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
2026/08/08 09:01 upstream 9a143525f62b e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
2026/08/07 04:06 upstream 0d8395707651 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
2026/08/07 02:45 upstream 0d8395707651 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
2026/08/05 16:03 upstream c21bb4193868 b3eac40e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
2026/08/05 04:21 upstream c21bb4193868 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
2026/08/04 14:43 upstream 848acc8ffe1b d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
* Struck through repros no longer work on HEAD.