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BUG: KMSAN: uninit-value in eth_type_trans+0x4ab/0x970 net/ethernet/eth.c:168
CPU: 0 PID: 2794 Comm: syz-executor2 Not tainted 4.17.0+ #8
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+0x185/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1122
 __msan_warning_32+0x70/0xc0 mm/kmsan/kmsan_instr.c:620
 eth_type_trans+0x4ab/0x970 net/ethernet/eth.c:168
 tun_get_user+0x4928/0x7f00 drivers/net/tun.c:1899
 tun_chr_write_iter+0x1d4/0x330 drivers/net/tun.c:1998
 call_write_iter include/linux/fs.h:1784 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x808/0x9f0 fs/read_write.c:487
 __kernel_write+0x201/0x5c0 fs/read_write.c:506
 write_pipe_buf+0x1d5/0x270 fs/splice.c:797
 splice_from_pipe_feed fs/splice.c:502 [inline]
 __splice_from_pipe+0x4a5/0xf50 fs/splice.c:626
 splice_from_pipe fs/splice.c:661 [inline]
 default_file_splice_write+0x1d9/0x380 fs/splice.c:809
 do_splice_from fs/splice.c:851 [inline]
 direct_splice_actor+0x19e/0x200 fs/splice.c:1018
 splice_direct_to_actor+0x767/0x1040 fs/splice.c:973
 do_splice_direct+0x335/0x540 fs/splice.c:1061
 do_sendfile+0x107b/0x1e40 fs/read_write.c:1440
 __do_sys_sendfile64 fs/read_write.c:1495 [inline]
 __se_sys_sendfile64 fs/read_write.c:1487 [inline]
 __x64_sys_sendfile64+0x218/0x390 fs/read_write.c:1487
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x455b29
RSP: 002b:00007f82ba395c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f82ba3966d4 RCX: 0000000000455b29
RDX: 0000000020d83ff8 RSI: 0000000000000015 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 00008000fffffffe R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004c0acd R14: 00000000004d0480 R15: 0000000000000000

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:294 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:686
 kmsan_memcpy_origins+0x11d/0x170 mm/kmsan/kmsan.c:527
 __msan_memcpy+0x109/0x160 mm/kmsan/kmsan_instr.c:413
 _copy_from_iter+0xf17/0x1d30 lib/iov_iter.c:591
 copy_from_iter include/linux/uio.h:115 [inline]
 skb_copy_datagram_from_iter+0x208/0xcd0 net/core/datagram.c:521
 tun_get_user+0x39b7/0x7f00 drivers/net/tun.c:1849
 tun_chr_write_iter+0x1d4/0x330 drivers/net/tun.c:1998
 call_write_iter include/linux/fs.h:1784 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x808/0x9f0 fs/read_write.c:487
 __kernel_write+0x201/0x5c0 fs/read_write.c:506
 write_pipe_buf+0x1d5/0x270 fs/splice.c:797
 splice_from_pipe_feed fs/splice.c:502 [inline]
 __splice_from_pipe+0x4a5/0xf50 fs/splice.c:626
 splice_from_pipe fs/splice.c:661 [inline]
 default_file_splice_write+0x1d9/0x380 fs/splice.c:809
 do_splice_from fs/splice.c:851 [inline]
 direct_splice_actor+0x19e/0x200 fs/splice.c:1018
 splice_direct_to_actor+0x767/0x1040 fs/splice.c:973
 do_splice_direct+0x335/0x540 fs/splice.c:1061
 do_sendfile+0x107b/0x1e40 fs/read_write.c:1440
 __do_sys_sendfile64 fs/read_write.c:1495 [inline]
 __se_sys_sendfile64 fs/read_write.c:1487 [inline]
 __x64_sys_sendfile64+0x218/0x390 fs/read_write.c:1487
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:816
 kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:886
 __alloc_pages_nodemask+0xf7b/0x5cc0 mm/page_alloc.c:4402
 alloc_pages_current+0x6b1/0x970 mm/mempolicy.c:2093
 alloc_pages include/linux/gfp.h:494 [inline]
 __page_cache_alloc+0x95/0x320 mm/filemap.c:946
 page_cache_alloc include/linux/pagemap.h:234 [inline]
 generic_file_buffered_read mm/filemap.c:2273 [inline]
 generic_file_read_iter+0x22a4/0x44d0 mm/filemap.c:2362
 call_read_iter include/linux/fs.h:1778 [inline]
 generic_file_splice_read+0x5d7/0x900 fs/splice.c:307
 do_splice_to fs/splice.c:880 [inline]
 splice_direct_to_actor+0x4cb/0x1040 fs/splice.c:952
 do_splice_direct+0x335/0x540 fs/splice.c:1061
 do_sendfile+0x107b/0x1e40 fs/read_write.c:1440
 __do_sys_sendfile64 fs/read_write.c:1495 [inline]
 __se_sys_sendfile64 fs/read_write.c:1487 [inline]
 __x64_sys_sendfile64+0x218/0x390 fs/read_write.c:1487
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
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