syzbot has found a reproducer for the following issue on: HEAD commit: 4aacf509e537 net: mv643xx: fix OF node refcount git tree: net console output: https://syzkaller.appspot.com/x/log.txt?x=15b8fdd2580000 kernel config: https://syzkaller.appspot.com/x/.config?x=65472e27d1590a04 dashboard link: https://syzkaller.appspot.com/bug?extid=83181a31faf9455499c5 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10a6da86580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13a3c0ae580000
Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/7559c887601e/disk-4aacf509.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/185ea069b480/vmlinux-4aacf509.xz kernel image: https://storage.googleapis.com/syzbot-assets/4285524349b9/bzImage-4aacf509.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: [email protected] ================================================================== BUG: KASAN: use-after-free in __tcp_hdrlen include/linux/tcp.h:31 [inline] BUG: KASAN: use-after-free in qdisc_pkt_len_segs_init+0x7f8/0xa30 net/core/dev.c:4140 Read of size 2 at addr ffff88817cd41734 by task syz.0.17/5856 CPU: 0 UID: 0 PID: 5856 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Call Trace: <IRQ> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description+0x55/0x1e0 mm/kasan/report.c:378 print_report+0x58/0x70 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 __tcp_hdrlen include/linux/tcp.h:31 [inline] qdisc_pkt_len_segs_init+0x7f8/0xa30 net/core/dev.c:4140 __dev_queue_xmit+0x29a/0x3950 net/core/dev.c:4782 dev_queue_xmit include/linux/netdevice.h:3418 [inline] hsr_xmit net/hsr/hsr_forward.c:440 [inline] hsr_forward_do net/hsr/hsr_forward.c:581 [inline] hsr_forward_skb+0x167e/0x2ab0 net/hsr/hsr_forward.c:743 hsr_handle_frame+0x6b8/0xa50 net/hsr/hsr_slave.c:81 __netif_receive_skb_core+0x98f/0x3170 net/core/dev.c:6089 __netif_receive_skb_list_core+0x24d/0x810 net/core/dev.c:6277 __netif_receive_skb_list net/core/dev.c:6344 [inline] netif_receive_skb_list_internal+0x995/0xcf0 net/core/dev.c:6435 gro_normal_list include/net/gro.h:523 [inline] gro_flush_normal include/net/gro.h:531 [inline] napi_complete_done+0x299/0x730 net/core/dev.c:6803 gro_cell_poll+0x5a9/0x5d0 net/core/gro_cells.c:74 __napi_poll+0xae/0x340 net/core/dev.c:7733 napi_poll net/core/dev.c:7796 [inline] net_rx_action+0x627/0xf70 net/core/dev.c:7953 handle_softirqs+0x22a/0x840 kernel/softirq.c:622 do_softirq+0x76/0xd0 kernel/softirq.c:523 </IRQ> <TASK> __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450 local_bh_enable include/linux/bottom_half.h:33 [inline] tun_rx_batched+0x617/0x790 drivers/net/tun.c:-1 tun_get_user+0x2bbc/0x43e0 drivers/net/tun.c:1955 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:2001 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x61d/0xb90 fs/read_write.c:688 ksys_write+0x150/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe91fb9ce59 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffda826a2e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fe91fe15fa0 RCX: 00007fe91fb9ce59 RDX: 000000000000007a RSI: 00002000000002c0 RDI: 0000000000000005 RBP: 00007fe91fc32d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fe91fe15fac R14: 00007fe91fe15fa0 R15: 00007fe91fe15fa0 </TASK> The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x17cd41 flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff) raw: 057ff00000000000 ffffea0005f35048 ffffea0005f35048 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner info is not present (never set?) Memory state around the buggy address: ffff88817cd41600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88817cd41680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff88817cd41700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88817cd41780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88817cd41800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== --- 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.
