[syzbot] [net?] KMSAN: uninit-value in gre_rcv (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    962490525cff Merge tag 'probes-fixes-v6.9-rc1' of git://gi..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10f20ed9180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e2599baf258ef795
dashboard link: https://syzkaller.appspot.com/bug?extid=1c1cf138518bf0c53d68
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13686595180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10581231180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ef3aa69f9748/disk-96249052.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/258fffe9afb1/vmlinux-96249052.xz
kernel image: https://storage.googleapis.com/syzbot-assets/56345f303e67/bzImage-96249052.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1c1cf138518bf0c53d68@xxxxxxxxxxxxxxxxxxxxxxxxx

syz-executor114 uses obsolete (PF_INET,SOCK_PACKET)
=====================================================
BUG: KMSAN: uninit-value in pskb_may_pull_reason include/linux/skbuff.h:2742 [inline]
BUG: KMSAN: uninit-value in pskb_may_pull include/linux/skbuff.h:2756 [inline]
BUG: KMSAN: uninit-value in ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline]
BUG: KMSAN: uninit-value in gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610
 pskb_may_pull_reason include/linux/skbuff.h:2742 [inline]
 pskb_may_pull include/linux/skbuff.h:2756 [inline]
 ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline]
 gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610
 ip6_protocol_deliver_rcu+0x1d4c/0x2ca0 net/ipv6/ip6_input.c:438
 ip6_input_finish net/ipv6/ip6_input.c:483 [inline]
 NF_HOOK include/linux/netfilter.h:314 [inline]
 ip6_input+0x15d/0x430 net/ipv6/ip6_input.c:492
 ip6_mc_input+0xa7e/0xc80 net/ipv6/ip6_input.c:586
 dst_input include/net/dst.h:460 [inline]
 ip6_rcv_finish+0x955/0x970 net/ipv6/ip6_input.c:79
 NF_HOOK include/linux/netfilter.h:314 [inline]
 ipv6_rcv+0xde/0x390 net/ipv6/ip6_input.c:310
 __netif_receive_skb_one_core net/core/dev.c:5538 [inline]
 __netif_receive_skb+0x1da/0xa00 net/core/dev.c:5652
 netif_receive_skb_internal net/core/dev.c:5738 [inline]
 netif_receive_skb+0x58/0x660 net/core/dev.c:5798
 tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1549
 tun_get_user+0x5566/0x69e0 drivers/net/tun.c:2002
 tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2108 [inline]
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xb63/0x1520 fs/read_write.c:590
 ksys_write+0x20f/0x4c0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x93/0xe0 fs/read_write.c:652
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:3804 [inline]
 slab_alloc_node mm/slub.c:3845 [inline]
 kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888
 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577
 __alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1318 [inline]
 alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6504
 sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2795
 tun_alloc_skb drivers/net/tun.c:1525 [inline]
 tun_get_user+0x209a/0x69e0 drivers/net/tun.c:1846
 tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2108 [inline]
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xb63/0x1520 fs/read_write.c:590
 ksys_write+0x20f/0x4c0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x93/0xe0 fs/read_write.c:652
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

CPU: 1 PID: 5045 Comm: syz-executor114 Not tainted 6.9.0-rc1-syzkaller-00021-g962490525cff #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
=====================================================


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