From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f198.google.com (mail-oi1-f198.google.com [209.85.167.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3C350353A8A for ; Sun, 16 Aug 2026 13:45:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786887937; cv=none; b=MkpEk0E8YZbD8+k/SOPWcufaKeQdkVcGMfse+aiW7B+pA5+ZOxekqwOHzY5L2lzT9cYK9yi2Tra3JOQJ+w5h4mMQgqMzBY1POgz4Dj4tj6p3fhufezJF6okphaRb6ksdfju8L1qZPNTVOTnxek88jCCph7CGlUnfk9eKmNRXw94= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786887937; c=relaxed/simple; bh=Du/vOM0bE9iJZfH//3Dxe+lDliwwSlmnC3zcoSENi+w=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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2002:a05:6808:690b:b0:4ae:f5be:fe29 with SMTP id 5614622812f47-4b241917e16mr19106105b6e.5.1786887933926; Sun, 16 Aug 2026 06:45:33 -0700 (PDT) Date: Sun, 16 Aug 2026 06:45:33 -0700 In-Reply-To: <6a57ad78.9d83364e.246513.0004.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a81befd.dbb3a75c.20434b.0030.GAE@google.com> Subject: Re: [syzbot] [net?] KASAN: slab-use-after-free Read in llc_conn_ac_send_sabme_cmd_p_set_x From: syzbot To: davem@davemloft.net, edumazet@google.com, horms@kernel.org, jeffinphilip14@gmail.com, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 3eb40771c00a Merge tag 'soc-fixes-7.2-3' of git://git.kern.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13e296c6580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1d67342c314f228d dashboard link: https://syzkaller.appspot.com/bug?extid=44efda9647c52be29d9c 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=109f1949580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+44efda9647c52be29d9c@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in llc_conn_ac_send_sabme_cmd_p_set_x+0x442/0x470 net/llc/llc_c_ac.c:782 Read of size 1 at addr ffff888058d87010 by task syz-executor377/6034 CPU: 3 UID: 0 PID: 6034 Comm: syz-executor377 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __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 llc_conn_ac_send_sabme_cmd_p_set_x+0x442/0x470 net/llc/llc_c_ac.c:782 llc_exec_conn_trans_actions net/llc/llc_conn.c:437 [inline] llc_conn_service net/llc/llc_conn.c:362 [inline] llc_conn_state_process+0x3ec/0x1480 net/llc/llc_conn.c:66 llc_process_tmr_ev net/llc/llc_c_ac.c:1442 [inline] llc_conn_tmr_common_cb+0x2d4/0x880 net/llc/llc_c_ac.c:1325 call_timer_fn+0x19a/0x610 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers+0x757/0xb00 kernel/time/timer.c:2374 __run_timer_base kernel/time/timer.c:2386 [inline] __run_timer_base kernel/time/timer.c:2378 [inline] run_timer_base+0x114/0x190 kernel/time/timer.c:2395 run_timer_softirq+0x1a/0x50 kernel/time/timer.c:2405 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_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:preempt_count_sub+0x0/0x160 kernel/sched/core.c:6004 Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 c7 c7 e0 bd 8a 94 e9 10 95 71 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1e fa 48 c7 c0 00 96 93 9b 53 89 fb 48 ba 00 00 00 00 00 fc RSP: 0018:ffffc900016bfda8 EFLAGS: 00000246 RAX: 0000000000000001 RBX: ffff88803d884380 RCX: ffffffff81e65993 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000001 RBP: 1ffff920002d7fba R08: 0000000000000000 R09: ffffed1007b10870 R10: ffff88803d884383 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 __raw_spin_unlock include/linux/spinlock_api_smp.h:169 [inline] _raw_spin_unlock+0x28/0x50 kernel/locking/spinlock.c:190 spin_unlock include/linux/spinlock.h:390 [inline] setfl fs/fcntl.c:85 [inline] do_fcntl+0x5da/0x1670 fs/fcntl.c:477 __do_sys_fcntl fs/fcntl.c:602 [inline] __se_sys_fcntl fs/fcntl.c:587 [inline] __x64_sys_fcntl+0x163/0x200 fs/fcntl.c:587 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: 0033:0x7ff89b73ab00 Code: 00 00 0f 1f 84 00 00 00 00 00 48 83 ec 18 64 48 8b 04 25 28 00 00 00 48 89 44 24 08 31 c0 83 fe 09 74 27 b8 48 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 40 48 8b 54 24 08 64 48 2b 14 25 28 00 00 00 RSP: 002b:00007ff8986ff130 EFLAGS: 00000293 ORIG_RAX: 0000000000000048 RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007ff89b73ab00 RDX: 0000000000000802 RSI: 0000000000000004 RDI: 0000000000000006 RBP: 000000000000005c R08: 0000000000000004 R09: 0000000000000017 R10: 00007ff8986ff1b4 R11: 0000000000000293 R12: 0000000000000007 R13: 0000000000000022 R14: 0000000088888889 R15: 000000000000002e Allocated by task 6032: 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] llc_sap_alloc net/llc/llc_core.c:29 [inline] llc_sap_open+0x120/0x3b0 net/llc/llc_core.c:96 llc_ui_bind+0xb67/0xe40 net/llc/af_llc.c:386 __sys_bind_socket net/socket.c:1920 [inline] __sys_bind_socket net/socket.c:1912 [inline] __sys_bind+0x1a9/0x260 net/socket.c:1951 __do_sys_bind net/socket.c:1956 [inline] __se_sys_bind net/socket.c:1954 [inline] __x64_sys_bind+0x72/0xb0 net/socket.c:1954 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 33: 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 run_ksoftirqd kernel/softirq.c:1076 [inline] run_ksoftirqd+0x38/0x60 kernel/softirq.c:1068 smpboot_thread_fn+0x3d3/0xaa0 kernel/smpboot.c:160 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 The buggy address belongs to the object at ffff888058d87000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 16 bytes inside of freed 2048-byte region [ffff888058d87000, ffff888058d87800) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x58d80 head: order:3 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 ffff88801c042f00 dead000000000100 dead000000000122 raw: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000 head: 00fff00000000040 ffff88801c042f00 dead000000000100 dead000000000122 head: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000 head: 00fff00000000003 fffffffffffffe01 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6028, tgid 6024 (syz-executor377), ts 76930678762, free_ts 76926318518 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] llc_sap_alloc net/llc/llc_core.c:29 [inline] llc_sap_open+0x120/0x3b0 net/llc/llc_core.c:96 llc_ui_bind+0xb67/0xe40 net/llc/af_llc.c:386 __sys_bind_socket net/socket.c:1920 [inline] __sys_bind_socket net/socket.c:1912 [inline] __sys_bind+0x1a9/0x260 net/socket.c:1951 __do_sys_bind net/socket.c:1956 [inline] __se_sys_bind net/socket.c:1954 [inline] __x64_sys_bind+0x72/0xb0 net/socket.c:1954 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 page last free pid 6028 tgid 6024 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 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4584 [inline] slab_alloc_node mm/slub.c:4917 [inline] __kmalloc_cache_noprof+0x265/0x6c0 mm/slub.c:5485 _kmalloc_noprof include/linux/slab.h:988 [inline] _kzalloc_noprof include/linux/slab.h:1309 [inline] ref_tracker_alloc+0x190/0x590 lib/ref_tracker.c:270 __netdev_tracker_alloc include/linux/netdevice.h:4496 [inline] netdev_tracker_alloc include/linux/netdevice.h:4508 [inline] llc_ui_bind+0x77b/0xe40 net/llc/af_llc.c:412 __sys_bind_socket net/socket.c:1920 [inline] __sys_bind_socket net/socket.c:1912 [inline] __sys_bind+0x1a9/0x260 net/socket.c:1951 __do_sys_bind net/socket.c:1956 [inline] __se_sys_bind net/socket.c:1954 [inline] __x64_sys_bind+0x72/0xb0 net/socket.c:1954 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: ffff888058d86f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888058d86f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888058d87000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888058d87080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888058d87100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ---------------- Code disassembly (best guess): 0: 90 nop 1: 90 nop 2: 90 nop 3: 90 nop 4: 90 nop 5: 90 nop 6: 90 nop 7: 90 nop 8: 90 nop 9: 90 nop a: f3 0f 1e fa endbr64 e: 48 c7 c7 e0 bd 8a 94 mov $0xffffffff948abde0,%rdi 15: e9 10 95 71 00 jmp 0x71952a 1a: 90 nop 1b: 90 nop 1c: 90 nop 1d: 90 nop 1e: 90 nop 1f: 90 nop 20: 90 nop 21: 90 nop 22: 90 nop 23: 90 nop 24: 90 nop 25: 90 nop 26: 90 nop 27: 90 nop 28: 90 nop 29: 90 nop * 2a: f3 0f 1e fa endbr64 <-- trapping instruction 2e: 48 c7 c0 00 96 93 9b mov $0xffffffff9b939600,%rax 35: 53 push %rbx 36: 89 fb mov %edi,%ebx 38: 48 rex.W 39: ba 00 00 00 00 mov $0x0,%edx 3e: 00 fc add %bh,%ah --- 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.