=====================================================
BUG: KMSAN: uninit-value in bpf_prog_run_generic_xdp+0x1a74/0x1ff0 net/core/dev.c:5206
 bpf_prog_run_generic_xdp+0x1a74/0x1ff0 net/core/dev.c:5206
 netif_receive_generic_xdp net/core/dev.c:5286 [inline]
 do_xdp_generic+0xd42/0x1680 net/core/dev.c:5348
 tun_get_user+0x4841/0x6a80 drivers/net/tun.c:1860
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1984
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0xb31/0x1560 fs/read_write.c:684
 ksys_write fs/read_write.c:736 [inline]
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __ia32_sys_write+0x1f9/0x4d0 fs/read_write.c:744
 ia32_sys_call+0x30f2/0x42c0 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+0xb0/0x110 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 stored to memory at:
 pskb_expand_head+0x313/0x1c90 net/core/skbuff.c:2255
 netif_skb_check_for_xdp net/core/dev.c:5249 [inline]
 netif_receive_generic_xdp net/core/dev.c:5280 [inline]
 do_xdp_generic+0xa69/0x1680 net/core/dev.c:5348
 tun_get_user+0x4841/0x6a80 drivers/net/tun.c:1860
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1984
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0xb31/0x1560 fs/read_write.c:684
 ksys_write fs/read_write.c:736 [inline]
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __ia32_sys_write+0x1f9/0x4d0 fs/read_write.c:744
 ia32_sys_call+0x30f2/0x42c0 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+0xb0/0x110 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:4167 [inline]
 slab_alloc_node mm/slub.c:4210 [inline]
 __do_kmalloc_node mm/slub.c:4340 [inline]
 __kmalloc_node_track_caller_noprof+0x96d/0x12f0 mm/slub.c:4360
 kmalloc_reserve+0x22f/0x4b0 net/core/skbuff.c:599
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1340 [inline]
 alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6639
 sock_alloc_send_pskb+0xad8/0xc70 net/core/sock.c:2954
 tun_alloc_skb drivers/net/tun.c:1461 [inline]
 tun_get_user+0x1013/0x6a80 drivers/net/tun.c:1782
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1984
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0xb31/0x1560 fs/read_write.c:684
 ksys_write fs/read_write.c:736 [inline]
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __ia32_sys_write+0x1f9/0x4d0 fs/read_write.c:744
 ia32_sys_call+0x30f2/0x42c0 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+0xb0/0x110 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

CPU: 1 UID: 0 PID: 7599 Comm: syz.7.414 Not tainted 6.15.0-rc3-syzkaller-00094-g02ddfb981de8 #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
=====================================================