[syzbot] [net?] KMSAN: uninit-value in __vxlan_find_mac

[syzbot <syzbot+35e7e2811bbe5777b20e@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    de2f378f2b77 Merge tag 'nfsd-6.12-4' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b170c0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e4580d62ee1893a5
dashboard link: https://syzkaller.appspot.com/bug?extid=35e7e2811bbe5777b20e
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f0ff1d637186/disk-de2f378f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1515128a919f/vmlinux-de2f378f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6624bf235bc6/bzImage-de2f378f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+35e7e2811bbe5777b20e@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in __vxlan_find_mac+0x497/0x4e0
 __vxlan_find_mac+0x497/0x4e0
 vxlan_find_mac drivers/net/vxlan/vxlan_core.c:436 [inline]
 vxlan_xmit+0x1669/0x39f0 drivers/net/vxlan/vxlan_core.c:2753
 __netdev_start_xmit include/linux/netdevice.h:4928 [inline]
 netdev_start_xmit include/linux/netdevice.h:4937 [inline]
 xmit_one net/core/dev.c:3588 [inline]
 dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3604
 __dev_queue_xmit+0x3562/0x56d0 net/core/dev.c:4432
 dev_queue_xmit include/linux/netdevice.h:3094 [inline]
 __bpf_tx_skb net/core/filter.c:2152 [inline]
 __bpf_redirect_common net/core/filter.c:2196 [inline]
 __bpf_redirect+0x148c/0x1610 net/core/filter.c:2203
 ____bpf_clone_redirect net/core/filter.c:2477 [inline]
 bpf_clone_redirect+0x37e/0x500 net/core/filter.c:2447
 ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:2010
 __bpf_prog_run512+0xc5/0xf0 kernel/bpf/core.c:2253
 bpf_dispatcher_nop_func include/linux/bpf.h:1265 [inline]
 __bpf_prog_run include/linux/filter.h:701 [inline]
 bpf_prog_run include/linux/filter.h:708 [inline]
 bpf_test_run+0x546/0xd20 net/bpf/test_run.c:434
 bpf_prog_test_run_skb+0x182f/0x24d0 net/bpf/test_run.c:1095
 bpf_prog_test_run+0x5e5/0xa30 kernel/bpf/syscall.c:4266
 __sys_bpf+0x6aa/0xd90 kernel/bpf/syscall.c:5671
 __do_sys_bpf kernel/bpf/syscall.c:5760 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5758 [inline]
 __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5758
 x64_sys_call+0x2cce/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4091 [inline]
 slab_alloc_node mm/slub.c:4134 [inline]
 kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4186
 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587
 pskb_expand_head+0x226/0x1a60 net/core/skbuff.c:2275
 skb_ensure_writable+0x496/0x520 net/core/skbuff.c:6214
 __bpf_try_make_writable net/core/filter.c:1677 [inline]
 bpf_try_make_writable net/core/filter.c:1683 [inline]
 bpf_try_make_head_writable net/core/filter.c:1691 [inline]
 ____bpf_clone_redirect net/core/filter.c:2471 [inline]
 bpf_clone_redirect+0x1c5/0x500 net/core/filter.c:2447
 ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:2010
 __bpf_prog_run512+0xc5/0xf0 kernel/bpf/core.c:2253
 bpf_dispatcher_nop_func include/linux/bpf.h:1265 [inline]
 __bpf_prog_run include/linux/filter.h:701 [inline]
 bpf_prog_run include/linux/filter.h:708 [inline]
 bpf_test_run+0x546/0xd20 net/bpf/test_run.c:434
 bpf_prog_test_run_skb+0x182f/0x24d0 net/bpf/test_run.c:1095
 bpf_prog_test_run+0x5e5/0xa30 kernel/bpf/syscall.c:4266
 __sys_bpf+0x6aa/0xd90 kernel/bpf/syscall.c:5671
 __do_sys_bpf kernel/bpf/syscall.c:5760 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5758 [inline]
 __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5758
 x64_sys_call+0x2cce/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 8041 Comm: syz.2.760 Not tainted 6.12.0-rc6-syzkaller-00279-gde2f378f2b77 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
=====================================================


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