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List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6602:6c1a:b0:929:68d0:d977 with SMTP id ca18e2360f4ac-93b96b5f8cfmr792037139f.17.1759635423250; Sat, 04 Oct 2025 20:37:03 -0700 (PDT) Date: Sat, 04 Oct 2025 20:37:03 -0700 In-Reply-To: <20251004225256.8119-1-hdanton@sina.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68e1e7df.a00a0220.102ee.0125.GAE@google.com> Subject: Re: [syzbot] [afs?] KASAN: slab-use-after-free Read in afs_dynroot_readdir (2) From: syzbot To: hdanton@sina.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: KASAN: slab-use-after-free Read in afs_dynroot_readdir ================================================================== BUG: KASAN: slab-use-after-free in afs_dynroot_readdir_cells fs/afs/dynroot.c:299 [inline] BUG: KASAN: slab-use-after-free in afs_dynroot_readdir+0x106f/0x12e0 fs/afs/dynroot.c:363 Read of size 4 at addr ffff88803504a148 by task syz.0.404/7214 CPU: 1 UID: 0 PID: 7214 Comm: syz.0.404 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xcd/0x630 mm/kasan/report.c:482 kasan_report+0xe0/0x110 mm/kasan/report.c:595 afs_dynroot_readdir_cells fs/afs/dynroot.c:299 [inline] afs_dynroot_readdir+0x106f/0x12e0 fs/afs/dynroot.c:363 iterate_dir+0x293/0xaf0 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:410 [inline] __se_sys_getdents64 fs/readdir.c:396 [inline] __x64_sys_getdents64+0x13c/0x2c0 fs/readdir.c:396 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f820038eec9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f820115a038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9 RAX: ffffffffffffffda RBX: 00007f82005e5fa0 RCX: 00007f820038eec9 RDX: 0000000000000055 RSI: 00002000000007c0 RDI: 0000000000000003 RBP: 00007f8200411f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f82005e6038 R14: 00007f82005e5fa0 R15: 00007ffd74cb1208 Allocated by task 7208: kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 kasan_save_track+0x14/0x30 mm/kasan/common.c:77 poison_kmalloc_redzone mm/kasan/common.c:400 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417 kmalloc_noprof include/linux/slab.h:957 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] afs_alloc_cell fs/afs/cell.c:137 [inline] afs_lookup_cell+0x61d/0x1680 fs/afs/cell.c:265 afs_dynroot_lookup_cell fs/afs/dynroot.c:111 [inline] afs_dynroot_lookup+0x3d8/0xd60 fs/afs/dynroot.c:159 __lookup_slow+0x251/0x460 fs/namei.c:1816 lookup_slow fs/namei.c:1833 [inline] walk_component+0x353/0x5b0 fs/namei.c:2151 lookup_last fs/namei.c:2652 [inline] path_lookupat+0x142/0x6d0 fs/namei.c:2676 filename_lookup+0x224/0x5f0 fs/namei.c:2705 do_linkat+0x14c/0x5a0 fs/namei.c:4991 __do_sys_link fs/namei.c:5045 [inline] __se_sys_link fs/namei.c:5043 [inline] __x64_sys_link+0x7d/0xa0 fs/namei.c:5043 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 0: kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 kasan_save_track+0x14/0x30 mm/kasan/common.c:77 __kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:587 kasan_save_free_info mm/kasan/kasan.h:406 [inline] poison_slab_object mm/kasan/common.c:252 [inline] __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:284 kasan_slab_free include/linux/kasan.h:234 [inline] slab_free_hook mm/slub.c:2514 [inline] slab_free mm/slub.c:6566 [inline] kfree+0x2b8/0x6d0 mm/slub.c:6773 afs_cell_destroy+0x1e2/0x2c0 fs/afs/cell.c:524 rcu_do_batch kernel/rcu/tree.c:2605 [inline] rcu_core+0x799/0x1530 kernel/rcu/tree.c:2861 handle_softirqs+0x219/0x8e0 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0x109/0x170 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline] sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1052 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 Last potentially related work creation: kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:559 __call_rcu_common.constprop.0+0xa5/0xa10 kernel/rcu/tree.c:3123 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3263 process_scheduled_works kernel/workqueue.c:3346 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Second to last potentially related work creation: kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:559 insert_work+0x36/0x230 kernel/workqueue.c:2186 __queue_work+0x97e/0x1160 kernel/workqueue.c:2341 queue_work_on+0x1a4/0x1f0 kernel/workqueue.c:2392 queue_work include/linux/workqueue.h:669 [inline] afs_unuse_cell+0x259/0x2e0 fs/afs/cell.c:621 __dentry_kill+0x23e/0x600 fs/dcache.c:674 dput.part.0+0x4b1/0x9b0 fs/dcache.c:911 dput+0x1f/0x30 fs/dcache.c:901 path_put fs/namei.c:626 [inline] do_linkat+0x320/0x5a0 fs/namei.c:5028 __do_sys_link fs/namei.c:5045 [inline] __se_sys_link fs/namei.c:5043 [inline] __x64_sys_link+0x7d/0xa0 fs/namei.c:5043 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88803504a000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 328 bytes inside of freed 1024-byte region [ffff88803504a000, ffff88803504a400) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x35048 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000040 ffff88801b026dc0 0000000000000000 dead000000000001 raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000 head: 00fff00000000040 ffff88801b026dc0 0000000000000000 dead000000000001 head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000 head: 00fff00000000003 ffffea0000d41201 00000000ffffffff 00000000ffffffff head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 3, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 3527, tgid 3527 (kworker/u8:9), ts 87582678068, free_ts 87538643162 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1850 prep_new_page mm/page_alloc.c:1858 [inline] get_page_from_freelist+0x10a3/0x3a30 mm/page_alloc.c:3884 __alloc_frozen_pages_noprof+0x25f/0x2470 mm/page_alloc.c:5183 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416 alloc_slab_page mm/slub.c:3030 [inline] allocate_slab mm/slub.c:3203 [inline] new_slab+0x24a/0x360 mm/slub.c:3257 ___slab_alloc+0xdc4/0x1ae0 mm/slub.c:4627 __slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4746 __slab_alloc_node mm/slub.c:4822 [inline] slab_alloc_node mm/slub.c:5233 [inline] __do_kmalloc_node mm/slub.c:5602 [inline] __kmalloc_noprof+0x501/0x880 mm/slub.c:5615 kmalloc_noprof include/linux/slab.h:961 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] neigh_alloc net/core/neighbour.c:522 [inline] ___neigh_create+0x14e6/0x28c0 net/core/neighbour.c:656 ip6_finish_output2+0x11aa/0x1cf0 net/ipv6/ip6_output.c:128 __ip6_finish_output+0x3cd/0x1010 net/ipv6/ip6_output.c:209 ip6_finish_output net/ipv6/ip6_output.c:220 [inline] NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x253/0x710 net/ipv6/ip6_output.c:247 dst_output include/net/dst.h:464 [inline] NF_HOOK include/linux/netfilter.h:318 [inline] ndisc_send_skb+0xa85/0x1f50 net/ipv6/ndisc.c:512 ndisc_send_ns+0xc6/0x140 net/ipv6/ndisc.c:670 addrconf_dad_work+0xbc9/0x14e0 net/ipv6/addrconf.c:4282 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3263 page last free pid 5935 tgid 5935 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1394 [inline] __free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2906 discard_slab mm/slub.c:3301 [inline] __put_partials+0x130/0x170 mm/slub.c:3848 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:352 kasan_slab_alloc include/linux/kasan.h:252 [inline] slab_post_alloc_hook mm/slub.c:4946 [inline] slab_alloc_node mm/slub.c:5245 [inline] kmem_cache_alloc_node_noprof+0x28a/0x770 mm/slub.c:5297 __alloc_skb+0x2b2/0x380 net/core/skbuff.c:660 alloc_skb include/linux/skbuff.h:1383 [inline] netlink_alloc_large_skb+0x69/0x140 net/netlink/af_netlink.c:1186 netlink_sendmsg+0x698/0xdd0 net/netlink/af_netlink.c:1871 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] __sys_sendto+0x4a0/0x520 net/socket.c:2244 __do_sys_sendto net/socket.c:2251 [inline] __se_sys_sendto net/socket.c:2247 [inline] __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2247 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff88803504a000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88803504a080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88803504a100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88803504a180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88803504a200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Tested on: commit: 6093a688 Merge tag 'char-misc-6.18-rc1' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=171a15cd980000 kernel config: https://syzkaller.appspot.com/x/.config?x=8f142ebe84501b0b dashboard link: https://syzkaller.appspot.com/bug?extid=ae8ad52680705c162471 compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=1485c458580000