From: syzbot <syzbot+c876adfab6362679008c@syzkaller.appspotmail.com>
To: davem@davemloft.net, dhowells@redhat.com, edumazet@google.com,
horms@kernel.org, kuba@kernel.org,
linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org,
marc.dionne@auristor.com, netdev@vger.kernel.org,
pabeni@redhat.com, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [afs?] [net?] KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers
Date: Mon, 10 Aug 2026 06:22:30 -0700 [thread overview]
Message-ID: <6a79d096.9c11d2ce.289b96.00ed.GAE@google.com> (raw)
In-Reply-To: <6a7919fe.9c11d2ce.289b96.00df.GAE@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: db2ddb871435 Linux 7.2-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=152cd079580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c44651ea7dd2f307
dashboard link: https://syzkaller.appspot.com/bug?extid=c876adfab6362679008c
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17e35132580000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c876adfab6362679008c@syzkaller.appspotmail.com
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
==================================================================
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
prev parent reply other threads:[~2026-08-10 13:22 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-10 0:23 [syzbot] [net?] [afs?] KASAN: slab-use-after-free Read in rxrpc_destroy_all_peers syzbot
2026-08-10 13:22 ` syzbot [this message]
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