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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+0xa51/0xb30 net/core/dev.c:4140
Read of size 2 at addr ffff8881236f93f4 by task syz.1.2375/14213

CPU: 3 UID: 0 PID: 14213 Comm: syz.1.2375 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <IRQ>
 __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/0x1d0 mm/kasan/report.c:595
 __tcp_hdrlen include/linux/tcp.h:31 [inline]
 qdisc_pkt_len_segs_init+0xa51/0xb30 net/core/dev.c:4140
 __dev_queue_xmit+0x270/0x4950 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+0xdcf/0x28a0 net/hsr/hsr_forward.c:743
 hsr_handle_frame+0x82f/0xac0 net/hsr/hsr_slave.c:81
 __netif_receive_skb_core.constprop.0+0x6c5/0x3530 net/core/dev.c:6089
 __netif_receive_skb_list_core+0x353/0x940 net/core/dev.c:6277
 __netif_receive_skb_list net/core/dev.c:6344 [inline]
 netif_receive_skb_list_internal+0x722/0xd40 net/core/dev.c:6435
 gro_normal_list include/net/gro.h:523 [inline]
 gro_normal_list include/net/gro.h:519 [inline]
 gro_flush_normal include/net/gro.h:531 [inline]
 napi_complete_done+0x221/0x940 net/core/dev.c:6803
 gro_cell_poll+0x46e/0x690 net/core/gro_cells.c:74
 __napi_poll.constprop.0+0xaf/0x450 net/core/dev.c:7733
 napi_poll net/core/dev.c:7796 [inline]
 net_rx_action+0xa40/0xf20 net/core/dev.c:7953
 handle_softirqs+0x1ea/0xa00 kernel/softirq.c:622
 do_softirq kernel/softirq.c:523 [inline]
 do_softirq+0xac/0xe0 kernel/softirq.c:510
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0xf8/0x120 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 tun_rx_batched.isra.0+0x407/0x750 drivers/net/tun.c:1512
 tun_get_user+0x1e31/0x3c20 drivers/net/tun.c:1955
 tun_chr_write_iter+0xdc/0x200 drivers/net/tun.c:2001
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5f73b9ce59
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:00007f5f749e8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f5f73e16090 RCX: 00007f5f73b9ce59
RDX: 000000000000fdef RSI: 00002000000002c0 RDI: 0000000000000006
RBP: 00007f5f73c32d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5f73e16128 R14: 00007f5f73e16090 R15: 00007ffc24277188
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1799 pfn:0x1236f9
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000001799 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 13358, tgid 13358 (syz.0.2141), ts 202157997463, free_ts 203312193940
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
 alloc_pages_mpol+0x1fb/0x540 mm/mempolicy.c:2490
 folio_alloc_mpol_noprof+0x36/0x260 mm/mempolicy.c:2509
 shmem_alloc_folio+0x135/0x160 mm/shmem.c:1933
 shmem_alloc_and_add_folio+0x371/0xd40 mm/shmem.c:1975
 shmem_get_folio_gfp+0x6ab/0x1900 mm/shmem.c:2564
 shmem_get_folio mm/shmem.c:2670 [inline]
 shmem_write_begin+0x1a4/0x420 mm/shmem.c:3303
 generic_perform_write+0x292/0xa40 mm/filemap.c:4325
 shmem_file_write_iter+0x10e/0x140 mm/shmem.c:3478
 __kernel_write_iter+0x2ac/0x920 fs/read_write.c:621
 dump_emit_page fs/coredump.c:1304 [inline]
 dump_user_range+0x3f9/0xad0 fs/coredump.c:1378
 elf_core_dump+0x2d5f/0x3d10 fs/binfmt_elf.c:2109
 coredump_write fs/coredump.c:1053 [inline]
 do_coredump fs/coredump.c:1132 [inline]
 vfs_coredump+0x29a0/0x5770 fs/coredump.c:1206
 get_signal+0x2162/0x2210 kernel/signal.c:3022
page last free pid 13358 tgid 13358 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 free_unref_folios+0xa0d/0x16f0 mm/page_alloc.c:3004
 folios_put_refs+0x571/0xa90 mm/swap.c:1008
 folio_batch_release include/linux/folio_batch.h:101 [inline]
 shmem_undo_range+0x5e5/0x1570 mm/shmem.c:1149
 shmem_truncate_range mm/shmem.c:1277 [inline]
 shmem_evict_inode+0x3f3/0xc40 mm/shmem.c:1407
 evict+0x3c2/0xad0 fs/inode.c:841
 iput_final fs/inode.c:1960 [inline]
 iput.part.0+0x605/0xf50 fs/inode.c:2009
 iput+0x35/0x40 fs/inode.c:1975
 dentry_unlink_inode+0x2c0/0x4c0 fs/dcache.c:476
 __dentry_kill+0x1d0/0x690 fs/dcache.c:718
 finish_dput+0x76/0x480 fs/dcache.c:927
 dput.part.0+0x456/0x570 fs/dcache.c:976
 dput+0x1f/0x30 fs/dcache.c:968
 __fput+0x519/0xb50 fs/file_table.c:518
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2af0 kernel/exit.c:976
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1119

Memory state around the buggy address:
 ffff8881236f9280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881236f9300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881236f9380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff8881236f9400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881236f9480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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