syz_tun: entered allmulticast mode
=====================================================
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in copy_to_user_iter lib/iov_iter.c:24 [inline]
BUG: KMSAN: kernel-infoleak in iterate_ubuf include/linux/iov_iter.h:30 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance include/linux/iov_iter.h:330 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0xef3/0x33f0 lib/iov_iter.c:197
 instrument_copy_to_user include/linux/instrumented.h:114 [inline]
 copy_to_user_iter lib/iov_iter.c:24 [inline]
 iterate_ubuf include/linux/iov_iter.h:30 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 _copy_to_iter+0xef3/0x33f0 lib/iov_iter.c:197
 copy_to_iter include/linux/uio.h:220 [inline]
 simple_copy_to_iter net/core/datagram.c:521 [inline]
 __skb_datagram_iter+0x196/0x12c0 net/core/datagram.c:402
 skb_copy_datagram_iter+0x5b/0x1e0 net/core/datagram.c:535
 skb_copy_datagram_msg include/linux/skbuff.h:4217 [inline]
 raw_recvmsg+0x2c8/0xab0 net/ipv4/raw.c:767
 inet_recvmsg+0x343/0x6a0 net/ipv4/af_inet.c:891
 sock_recvmsg_nosec net/socket.c:1078 [inline]
 sock_recvmsg+0x23c/0x390 net/socket.c:1100
 sock_read_iter+0x2c8/0x360 net/socket.c:1170
 io_iter_do_read io_uring/rw.c:827 [inline]
 __io_read+0xbf9/0x24b0 io_uring/rw.c:944
 io_read+0x6b/0x3c0 io_uring/rw.c:1024
 __io_issue_sqe+0x2bb/0x790 io_uring/io_uring.c:1792
 io_issue_sqe+0xae/0x1d00 io_uring/io_uring.c:1815
 io_queue_sqe io_uring/io_uring.c:2042 [inline]
 io_submit_sqe io_uring/io_uring.c:2320 [inline]
 io_submit_sqes+0x160f/0x3270 io_uring/io_uring.c:2434
 __do_sys_io_uring_enter io_uring/io_uring.c:3277 [inline]
 __se_sys_io_uring_enter+0x3b4/0x4bb0 io_uring/io_uring.c:3216
 __x64_sys_io_uring_enter+0x114/0x1a0 io_uring/io_uring.c:3216
 x64_sys_call+0x2ff7/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4955 [inline]
 slab_alloc_node mm/slub.c:5258 [inline]
 kmem_cache_alloc_node_noprof+0x9e7/0x17a0 mm/slub.c:5310
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:586
 __alloc_skb+0x866/0x10a0 net/core/skbuff.c:690
 alloc_skb include/linux/skbuff.h:1383 [inline]
 ipmr_cache_report+0x410/0x2200 net/ipv4/ipmr.c:1053
 ipmr_cache_unresolved+0x53d/0xd30 net/ipv4/ipmr.c:1153
 ip_mr_input+0xe78/0xfb0 net/ipv4/ipmr.c:2222
 dst_input include/net/dst.h:474 [inline]
 ip_rcv_finish+0x57a/0x5c0 net/ipv4/ip_input.c:453
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip_rcv+0xcb/0x380 net/ipv4/ip_input.c:573
 __netif_receive_skb_one_core net/core/dev.c:6137 [inline]
 __netif_receive_skb+0x312/0xac0 net/core/dev.c:6250
 netif_receive_skb_internal net/core/dev.c:6336 [inline]
 netif_receive_skb+0x57/0x630 net/core/dev.c:6395
 tun_rx_batched+0x1df/0x980 drivers/net/tun.c:1485
 tun_get_user+0x5c0e/0x6c60 drivers/net/tun.c:1953
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0xbe2/0x15d0 fs/read_write.c:686
 ksys_write fs/read_write.c:738 [inline]
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x1fb/0x4d0 fs/read_write.c:746
 x64_sys_call+0x30ab/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Bytes 26-31 of 32 are uninitialized
Memory access of size 32 starts at ffff88811b10a680
Data copied to user address 0000200000000280

CPU: 0 UID: 0 PID: 6251 Comm: syz.3.71 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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