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006d021491bc7-661179faf4bmr503534eaf.55.1768508784013; Thu, 15 Jan 2026 12:26:24 -0800 (PST) Date: Thu, 15 Jan 2026 12:26:23 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69694d6f.050a0220.58bed.0029.GAE@google.com> Subject: [syzbot] [hams?] BUG: unable to handle kernel paging request in sk_skb_reason_drop From: syzbot To: davem@davemloft.net, edumazet@google.com, horms@kernel.org, kuba@kernel.org, linux-hams@vger.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" Hello, syzbot found the following issue on: HEAD commit: 8bb886cb8f3a Merge tag 'edac_urgent_for_v6.18_rc5' of git:.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=175bf932580000 kernel config: https://syzkaller.appspot.com/x/.config?x=929790bc044e87d7 dashboard link: https://syzkaller.appspot.com/bug?extid=999115c3bf275797dc27 compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16d6a292580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12b5e342580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-8bb886cb.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/46fdb9b0b548/vmlinux-8bb886cb.xz kernel image: https://storage.googleapis.com/syzbot-assets/73268ceecbe7/bzImage-8bb886cb.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+999115c3bf275797dc27@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline] BUG: KASAN: slab-use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline] BUG: KASAN: slab-use-after-free in __refcount_sub_and_test include/linux/refcount.h:389 [inline] BUG: KASAN: slab-use-after-free in __refcount_dec_and_test include/linux/refcount.h:432 [inline] BUG: KASAN: slab-use-after-free in refcount_dec_and_test include/linux/refcount.h:450 [inline] BUG: KASAN: slab-use-after-free in skb_unref include/linux/skbuff.h:1292 [inline] BUG: KASAN: slab-use-after-free in __sk_skb_reason_drop net/core/skbuff.c:1175 [inline] BUG: KASAN: slab-use-after-free in sk_skb_reason_drop+0x37/0x170 net/core/skbuff.c:1203 Write of size 4 at addr ffff8880596605e4 by task syz.0.54/5600 CPU: 0 UID: 0 PID: 5600 Comm: syz.0.54 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xca/0x240 mm/kasan/report.c:482 kasan_report+0x118/0x150 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200 instrument_atomic_read_write include/linux/instrumented.h:96 [inline] atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline] __refcount_sub_and_test include/linux/refcount.h:389 [inline] __refcount_dec_and_test include/linux/refcount.h:432 [inline] refcount_dec_and_test include/linux/refcount.h:450 [inline] skb_unref include/linux/skbuff.h:1292 [inline] __sk_skb_reason_drop net/core/skbuff.c:1175 [inline] sk_skb_reason_drop+0x37/0x170 net/core/skbuff.c:1203 kfree_skb_reason include/linux/skbuff.h:1322 [inline] kfree_skb include/linux/skbuff.h:1331 [inline] nr_transmit_buffer+0x11d/0x1b0 net/netrom/nr_out.c:210 nr_establish_data_link+0x62/0xb0 net/netrom/nr_out.c:227 nr_connect+0x6e6/0xde0 net/netrom/af_netrom.c:723 __sys_connect_file net/socket.c:2102 [inline] __sys_connect+0x316/0x440 net/socket.c:2121 __do_sys_connect net/socket.c:2127 [inline] __se_sys_connect net/socket.c:2124 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2124 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe6a438f6c9 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:00007fe6a5268038 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 00007fe6a45e6090 RCX: 00007fe6a438f6c9 RDX: 0000000000000048 RSI: 0000200000000300 RDI: 0000000000000004 RBP: 00007fe6a4411f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fe6a45e6128 R14: 00007fe6a45e6090 R15: 00007ffdf569a138 Allocated by task 5600: kasan_save_stack mm/kasan/common.c:56 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:77 unpoison_slab_object mm/kasan/common.c:342 [inline] __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:368 kasan_slab_alloc include/linux/kasan.h:252 [inline] slab_post_alloc_hook mm/slub.c:4970 [inline] slab_alloc_node mm/slub.c:5280 [inline] kmem_cache_alloc_node_noprof+0x433/0x710 mm/slub.c:5332 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:660 alloc_skb include/linux/skbuff.h:1383 [inline] nr_write_internal+0xe2/0xc60 net/netrom/nr_subr.c:144 nr_establish_data_link+0x62/0xb0 net/netrom/nr_out.c:227 nr_connect+0x6e6/0xde0 net/netrom/af_netrom.c:723 __sys_connect_file net/socket.c:2102 [inline] __sys_connect+0x316/0x440 net/socket.c:2121 __do_sys_connect net/socket.c:2127 [inline] __se_sys_connect net/socket.c:2124 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2124 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 5600: kasan_save_stack mm/kasan/common.c:56 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:77 __kasan_save_free_info+0x46/0x50 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+0x5c/0x80 mm/kasan/common.c:284 kasan_slab_free include/linux/kasan.h:234 [inline] slab_free_hook mm/slub.c:2539 [inline] slab_free mm/slub.c:6630 [inline] kmem_cache_free+0x19b/0x690 mm/slub.c:6740 kfree_skb_reason include/linux/skbuff.h:1322 [inline] kfree_skb include/linux/skbuff.h:1331 [inline] nr_route_frame+0x467/0x7e0 net/netrom/nr_route.c:820 nr_transmit_buffer+0xe7/0x1b0 net/netrom/nr_out.c:209 nr_establish_data_link+0x62/0xb0 net/netrom/nr_out.c:227 nr_connect+0x6e6/0xde0 net/netrom/af_netrom.c:723 __sys_connect_file net/socket.c:2102 [inline] __sys_connect+0x316/0x440 net/socket.c:2121 __do_sys_connect net/socket.c:2127 [inline] __se_sys_connect net/socket.c:2124 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2124 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff888059660500 which belongs to the cache skbuff_head_cache of size 240 The buggy address is located 228 bytes inside of freed 240-byte region [ffff888059660500, ffff8880596605f0) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x59660 ksm flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 04fff00000000000 ffff8880304cfc80 ffffea00015cfa80 dead000000000003 raw: 0000000000000000 00000000800c000c 00000000f5000000 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 3035, tgid 3035 (kworker/u4:12), ts 243435803171, free_ts 243218050311 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1850 prep_new_page mm/page_alloc.c:1858 [inline] get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3884 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416 alloc_slab_page mm/slub.c:3055 [inline] allocate_slab+0x96/0x350 mm/slub.c:3228 new_slab mm/slub.c:3282 [inline] ___slab_alloc+0xe94/0x18a0 mm/slub.c:4651 __slab_alloc+0x65/0x100 mm/slub.c:4770 __slab_alloc_node mm/slub.c:4846 [inline] slab_alloc_node mm/slub.c:5268 [inline] kmem_cache_alloc_node_noprof+0x4c5/0x710 mm/slub.c:5332 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:660 alloc_skb include/linux/skbuff.h:1383 [inline] nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:763 [inline] nsim_dev_trap_report drivers/net/netdevsim/dev.c:820 [inline] nsim_dev_trap_report_work+0x29a/0xb80 drivers/net/netdevsim/dev.c:866 process_one_work kernel/workqueue.c:3263 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 page last free pid 5492 tgid 5492 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1394 [inline] __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2906 __slab_free+0x2e7/0x390 mm/slub.c:5962 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:352 kasan_slab_alloc include/linux/kasan.h:252 [inline] slab_post_alloc_hook mm/slub.c:4970 [inline] slab_alloc_node mm/slub.c:5280 [inline] kmem_cache_alloc_noprof+0x367/0x6e0 mm/slub.c:5287 ptlock_alloc+0x20/0x70 mm/memory.c:7284 ptlock_init include/linux/mm.h:3052 [inline] pagetable_pte_ctor include/linux/mm.h:3106 [inline] __pte_alloc_one_noprof include/asm-generic/pgalloc.h:78 [inline] pte_alloc_one+0x7a/0x310 arch/x86/mm/pgtable.c:18 do_fault_around mm/memory.c:5650 [inline] do_read_fault mm/memory.c:5689 [inline] do_fault mm/memory.c:5832 [inline] do_pte_missing mm/memory.c:4361 [inline] handle_pte_fault mm/memory.c:6177 [inline] __handle_mm_fault+0x2767/0x5400 mm/memory.c:6318 handle_mm_fault+0x40a/0x8e0 mm/memory.c:6487 do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 Memory state around the buggy address: ffff888059660480: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc ffff888059660500: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888059660580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc ^ ffff888059660600: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb ffff888059660680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title 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. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup