Zero length message leads to an empty skb ================================================================== BUG: KASAN: slab-use-after-free in ext4_read_inline_data+0x1c0/0x2a0 fs/ext4/inline.c:209 Read of size 68 at addr ffff88805eb7ac80 by task syz.0.174/6620 CPU: 0 PID: 6620 Comm: syz.0.174 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Call Trace: dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xa8/0x210 mm/kasan/report.c:468 kasan_report+0x117/0x150 mm/kasan/report.c:581 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x241/0x290 mm/kasan/generic.c:187 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105 ext4_read_inline_data+0x1c0/0x2a0 fs/ext4/inline.c:209 ext4_convert_inline_data_nolock+0x138/0x730 fs/ext4/inline.c:1214 ext4_try_add_inline_entry+0x73c/0xa70 fs/ext4/inline.c:1340 ext4_add_entry+0x5cc/0xd90 fs/ext4/namei.c:2458 ext4_mkdir+0x524/0xc90 fs/ext4/namei.c:3081 vfs_mkdir+0x2a5/0x470 fs/namei.c:4121 do_mkdirat+0x1dc/0x450 fs/namei.c:4144 __do_sys_mkdirat fs/namei.c:4159 [inline] __se_sys_mkdirat fs/namei.c:4157 [inline] __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4157 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fa33b19bcc7 Code: 00 66 90 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 db f7 ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 b8 02 01 00 00 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:00007fa3393f5e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000102 RAX: ffffffffffffffda RBX: 00007fa3393f5ee0 RCX: 00007fa33b19bcc7 RDX: 00000000000001ff RSI: 0000200000000080 RDI: 00000000ffffff9c RBP: 0000200000000140 R08: 0000200000000080 R09: 0000000000000000 R10: 0000200000000140 R11: 0000000000000246 R12: 0000200000000080 R13: 00007fa3393f5ea0 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 4519: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4e/0x70 mm/kasan/common.c:53 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329 kasan_slab_alloc include/linux/kasan.h:188 [inline] slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:767 slab_alloc_node mm/slub.c:3495 [inline] slab_alloc mm/slub.c:3503 [inline] __kmem_cache_alloc_lru mm/slub.c:3510 [inline] kmem_cache_alloc+0x17e/0x2c0 mm/slub.c:3519 skb_clone+0x1eb/0x370 net/core/skbuff.c:1912 batadv_iv_ogm_send_to_if net/batman-adv/bat_iv_ogm.c:381 [inline] batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:414 [inline] batadv_iv_send_outstanding_bat_ogm_packet+0x5b6/0x7d0 net/batman-adv/bat_iv_ogm.c:1783 process_one_work kernel/workqueue.c:2653 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 Freed by task 4519: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4e/0x70 mm/kasan/common.c:53 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237 kasan_slab_free include/linux/kasan.h:164 [inline] slab_free_hook mm/slub.c:1811 [inline] slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837 slab_free mm/slub.c:3830 [inline] kmem_cache_free+0xf8/0x290 mm/slub.c:3852 __netif_receive_skb_core+0x348e/0x3ab0 net/core/dev.c:5620 __netif_receive_skb_one_core net/core/dev.c:5644 [inline] __netif_receive_skb+0x74/0x290 net/core/dev.c:5760 process_backlog+0x380/0x710 net/core/dev.c:6088 __napi_poll+0xbb/0x460 net/core/dev.c:6650 napi_poll net/core/dev.c:6717 [inline] net_rx_action+0x65f/0xcc0 net/core/dev.c:6853 handle_softirqs+0x27d/0x820 kernel/softirq.c:578 do_softirq+0xfa/0x1a0 kernel/softirq.c:479 __local_bh_enable_ip+0x184/0x1c0 kernel/softirq.c:406 local_bh_enable include/linux/bottom_half.h:33 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:856 [inline] __dev_queue_xmit+0x1bc2/0x3630 net/core/dev.c:4490 dev_queue_xmit include/linux/netdevice.h:3113 [inline] batadv_send_skb_packet+0x3dd/0x660 net/batman-adv/send.c:108 batadv_iv_ogm_send_to_if net/batman-adv/bat_iv_ogm.c:386 [inline] batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:414 [inline] batadv_iv_send_outstanding_bat_ogm_packet+0x62d/0x7d0 net/batman-adv/bat_iv_ogm.c:1783 process_one_work kernel/workqueue.c:2653 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 The buggy address belongs to the object at ffff88805eb7ac80 which belongs to the cache skbuff_head_cache of size 240 The buggy address is located 0 bytes inside of freed 240-byte region [ffff88805eb7ac80, ffff88805eb7ad70) The buggy address belongs to the physical page: page:ffffea00017ade80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5eb7a flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff) page_type: 0xffffffff() raw: 00fff00000000800 ffff88801ea5f280 dead000000000122 0000000000000000 raw: 0000000000000000 00000000000c000c 00000001ffffffff 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 0x112820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 4519, tgid 4519 (kworker/u4:10), ts 226566225687, free_ts 226468523707 set_page_owner include/linux/page_owner.h:31 [inline] post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582 prep_new_page mm/page_alloc.c:1589 [inline] get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501 alloc_slab_page+0x5d/0x180 mm/slub.c:1881 allocate_slab mm/slub.c:2028 [inline] new_slab+0x87/0x2d0 mm/slub.c:2081 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253 __slab_alloc mm/slub.c:3339 [inline] __slab_alloc_node mm/slub.c:3392 [inline] slab_alloc_node mm/slub.c:3485 [inline] slab_alloc mm/slub.c:3503 [inline] __kmem_cache_alloc_lru mm/slub.c:3510 [inline] kmem_cache_alloc+0x109/0x2c0 mm/slub.c:3519 __build_skb net/core/skbuff.c:451 [inline] __netdev_alloc_skb+0x213/0x500 net/core/skbuff.c:743 __netdev_alloc_skb_ip_align include/linux/skbuff.h:3324 [inline] netdev_alloc_skb_ip_align include/linux/skbuff.h:3334 [inline] batadv_iv_ogm_aggregate_new net/batman-adv/bat_iv_ogm.c:557 [inline] batadv_iv_ogm_queue_add+0x833/0xdb0 net/batman-adv/bat_iv_ogm.c:673 batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:866 [inline] batadv_iv_ogm_schedule+0xba1/0x1080 net/batman-adv/bat_iv_ogm.c:898 batadv_iv_send_outstanding_bat_ogm_packet+0x6bf/0x7d0 net/batman-adv/bat_iv_ogm.c:1795 process_one_work kernel/workqueue.c:2653 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1182 [inline] free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459 tlb_batch_list_free mm/mmu_gather.c:115 [inline] tlb_finish_mmu+0x13e/0x220 mm/mmu_gather.c:428 exit_mmap+0x428/0xb90 mm/mmap.c:3315 __mmput+0x118/0x3a0 kernel/fork.c:1357 exit_mm+0x23f/0x340 kernel/exit.c:570 do_exit+0x909/0x2530 kernel/exit.c:871 do_group_exit+0x22d/0x2f0 kernel/exit.c:1026 get_signal+0x12a6/0x1390 kernel/signal.c:2903 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210 irqentry_exit_to_user_mode+0x9/0x30 kernel/entry/common.c:315 exc_page_fault+0x8c/0x100 arch/x86/mm/fault.c:1519 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608 Memory state around the buggy address: ffff88805eb7ab80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88805eb7ac00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc >ffff88805eb7ac80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88805eb7ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc ffff88805eb7ad80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb ==================================================================