syzbot

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BUG: KCSAN: data-race in __ip_make_skb / __ip_make_skb

read to 0xffff88816e817daa of 2 bytes by task 20216 on cpu 1:
 ip_select_ident_segs include/net/ip.h:541 [inline]
 ip_select_ident include/net/ip.h:556 [inline]
 __ip_make_skb+0x817/0xc70 net/ipv4/ip_output.c:1446
 ip_make_skb+0x233/0x2c0 net/ipv4/ip_output.c:1560
 udp_sendmsg+0x1199/0x1250 net/ipv4/udp.c:1260
 inet_sendmsg+0x63/0x80 net/ipv4/af_inet.c:830
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg net/socket.c:748 [inline]
 ____sys_sendmsg+0x37c/0x4d0 net/socket.c:2494
 ___sys_sendmsg net/socket.c:2548 [inline]
 __sys_sendmmsg+0x269/0x500 net/socket.c:2634
 __do_sys_sendmmsg net/socket.c:2663 [inline]
 __se_sys_sendmmsg net/socket.c:2660 [inline]
 __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2660
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read-write to 0xffff88816e817daa of 2 bytes by task 20212 on cpu 0:
 ip_select_ident_segs include/net/ip.h:542 [inline]
 ip_select_ident include/net/ip.h:556 [inline]
 __ip_make_skb+0x844/0xc70 net/ipv4/ip_output.c:1446
 ip_make_skb+0x233/0x2c0 net/ipv4/ip_output.c:1560
 udp_sendmsg+0x1199/0x1250 net/ipv4/udp.c:1260
 inet_sendmsg+0x63/0x80 net/ipv4/af_inet.c:830
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg net/socket.c:748 [inline]
 ____sys_sendmsg+0x37c/0x4d0 net/socket.c:2494
 ___sys_sendmsg net/socket.c:2548 [inline]
 __sys_sendmmsg+0x269/0x500 net/socket.c:2634
 __do_sys_sendmmsg net/socket.c:2663 [inline]
 __se_sys_sendmmsg net/socket.c:2660 [inline]
 __x64_sys_sendmmsg+0x57/0x60 net/socket.c:2660
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0ed4 -> 0x0ed5

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20212 Comm: syz-executor.2 Not tainted 6.5.0-rc7-syzkaller-00024-g93f5de5f648d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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