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:185
 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:185
 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:766
 inet_recvmsg+0x343/0x6a0 net/ipv4/af_inet.c:885
 sock_recvmsg_nosec net/socket.c:1078 [inline]
 sock_recvmsg+0x23c/0x390 net/socket.c:1100
 __sys_recvfrom+0x282/0x550 net/socket.c:2294
 __compat_sys_recvfrom net/compat.c:389 [inline]
 __do_compat_sys_recvfrom net/compat.c:402 [inline]
 __se_compat_sys_recvfrom net/compat.c:398 [inline]
 __ia32_compat_sys_recvfrom+0x13b/0x210 net/compat.c:398
 ia32_sys_call+0x1396/0x4310 arch/x86/include/generated/asm/syscalls_32.h:372
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xb0/0x150 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:369
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4985 [inline]
 slab_alloc_node mm/slub.c:5288 [inline]
 kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5340
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
 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:6079 [inline]
 __netif_receive_skb+0x312/0xac0 net/core/dev.c:6192
 netif_receive_skb_internal net/core/dev.c:6278 [inline]
 netif_receive_skb+0x57/0x630 net/core/dev.c:6337
 tun_rx_batched+0x1df/0x980 drivers/net/tun.c:1485
 tun_get_user+0x5d62/0x6d70 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]
 __ia32_sys_write+0x1f9/0x4d0 fs/read_write.c:746
 ia32_sys_call+0x35bc/0x4310 arch/x86/include/generated/asm/syscalls_32.h:5
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xb0/0x150 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:369
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Bytes 22-27 of 28 are uninitialized
Memory access of size 28 starts at ffff888118c7cb00
Data copied to user address 0000000080000300

CPU: 0 UID: 0 PID: 20401 Comm: syz.9.5050 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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