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BUG: KMSAN: uninit-value in packet_rcv_fanout+0x2442/0x25c0 net/packet/af_packet.c:1463
CPU: 1 PID: 21458 Comm: syz-executor.0 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1df/0x240 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
 packet_rcv_fanout+0x2442/0x25c0 net/packet/af_packet.c:1463
 deliver_skb net/core/dev.c:2247 [inline]
 deliver_ptype_list_skb net/core/dev.c:2262 [inline]
 __netif_receive_skb_core+0x3e02/0x5890 net/core/dev.c:5232
 __netif_receive_skb_one_core net/core/dev.c:5279 [inline]
 __netif_receive_skb net/core/dev.c:5395 [inline]
 netif_receive_skb_internal net/core/dev.c:5497 [inline]
 netif_receive_skb+0x56c/0xff0 net/core/dev.c:5556
 tun_rx_batched include/linux/skbuff.h:4327 [inline]
 tun_get_user+0x6df8/0x72f0 drivers/net/tun.c:1972
 tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2001
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0xd98/0x1480 fs/read_write.c:578
 ksys_write+0x267/0x450 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:640
 __ia32_sys_write+0x4a/0x70 fs/read_write.c:640
 do_syscall_32_irqs_on arch/x86/entry/common.c:430 [inline]
 __do_fast_syscall_32+0x2aa/0x400 arch/x86/entry/common.c:477
 do_fast_syscall_32+0x6b/0xd0 arch/x86/entry/common.c:505
 do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:554
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7f5d549
Code: Bad RIP value.
RSP: 002b:00000000f5d580c4 EFLAGS: 00000296 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 00000000000000f0 RCX: 00000000200004c0
RDX: 000000000000007a RSI: 0000000000028520 RDI: 000000000819af60
RBP: 00000000f5d58228 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:310
 __msan_chain_origin+0x50/0x90 mm/kmsan/kmsan_instr.c:165
 ___bpf_prog_run+0x6c64/0x97a0 kernel/bpf/core.c:1391
 __bpf_prog_run32+0x101/0x170 kernel/bpf/core.c:1681
 bpf_dispatcher_nop_func include/linux/bpf.h:556 [inline]
 bpf_prog_run_pin_on_cpu include/linux/filter.h:597 [inline]
 bpf_prog_run_clear_cb include/linux/filter.h:719 [inline]
 fanout_demux_bpf net/packet/af_packet.c:1404 [inline]
 packet_rcv_fanout+0x51e/0x25c0 net/packet/af_packet.c:1456
 deliver_skb net/core/dev.c:2247 [inline]
 deliver_ptype_list_skb net/core/dev.c:2262 [inline]
 __netif_receive_skb_core+0x3e02/0x5890 net/core/dev.c:5232
 __netif_receive_skb_one_core net/core/dev.c:5279 [inline]
 __netif_receive_skb net/core/dev.c:5395 [inline]
 netif_receive_skb_internal net/core/dev.c:5497 [inline]
 netif_receive_skb+0x56c/0xff0 net/core/dev.c:5556
 tun_rx_batched include/linux/skbuff.h:4327 [inline]
 tun_get_user+0x6df8/0x72f0 drivers/net/tun.c:1972
 tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2001
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0xd98/0x1480 fs/read_write.c:578
 ksys_write+0x267/0x450 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:640
 __ia32_sys_write+0x4a/0x70 fs/read_write.c:640
 do_syscall_32_irqs_on arch/x86/entry/common.c:430 [inline]
 __do_fast_syscall_32+0x2aa/0x400 arch/x86/entry/common.c:477
 do_fast_syscall_32+0x6b/0xd0 arch/x86/entry/common.c:505
 do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:554
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Local variable ----regs@__bpf_prog_run32 created at:
 __bpf_prog_run32+0x87/0x170 kernel/bpf/core.c:1681
 __bpf_prog_run32+0x87/0x170 kernel/bpf/core.c:1681
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