Hello,

syzbot found the following crash on:

HEAD commit: 686a4f77 kmsan: don't compile memmove git tree: https://github.com/google/kmsan.git master console output: https://syzkaller.appspot.com/x/log.txt?x=10b1da4ee00000 kernel config: https://syzkaller.appspot.com/x/.config?x=e10654781bc1f11c dashboard link: https://syzkaller.appspot.com/bug?extid=37bad4f9cb2033876f32 compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=102be0a1e00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=123105a5e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+37bad4f9cb2033876f32@syzkaller.appspotmail.com

===================================================== BUG: KMSAN: uninit-value in batadv_bla_tx+0x2675/0x3730 net/batman-adv/bridge_loop_avoidance.c:1960 CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.5.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x220 lib/dump_stack.c:118 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215 batadv_bla_tx+0x2675/0x3730 net/batman-adv/bridge_loop_avoidance.c:1960 batadv_interface_tx+0x67c/0x2450 net/batman-adv/soft-interface.c:239 __netdev_start_xmit include/linux/netdevice.h:4447 [inline] netdev_start_xmit include/linux/netdevice.h:4461 [inline] xmit_one net/core/dev.c:3420 [inline] dev_hard_start_xmit+0x531/0xab0 net/core/dev.c:3436 __dev_queue_xmit+0x37de/0x4220 net/core/dev.c:4013 dev_queue_xmit+0x4b/0x60 net/core/dev.c:4046 hsr_xmit net/hsr/hsr_forward.c:228 [inline] hsr_forward_do net/hsr/hsr_forward.c:285 [inline] hsr_forward_skb+0x2614/0x30d0 net/hsr/hsr_forward.c:361 hsr_handle_frame+0x385/0x4b0 net/hsr/hsr_slave.c:43 __netif_receive_skb_core+0x21de/0x5840 net/core/dev.c:5051 __netif_receive_skb_one_core net/core/dev.c:5148 [inline] __netif_receive_skb net/core/dev.c:5264 [inline] process_backlog+0x936/0x1410 net/core/dev.c:6095 napi_poll net/core/dev.c:6532 [inline] net_rx_action+0x786/0x1ab0 net/core/dev.c:6600 __do_softirq+0x311/0x83d kernel/softirq.c:293 run_ksoftirqd+0x25/0x40 kernel/softirq.c:607 smpboot_thread_fn+0x493/0x980 kernel/smpboot.c:165 kthread+0x4b5/0x4f0 kernel/kthread.c:256 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:353

Uninit was stored to memory at: kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline] kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:310 kmsan_memcpy_memmove_metadata+0x272/0x2e0 mm/kmsan/kmsan.c:247 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:267 __msan_memcpy+0x43/0x50 mm/kmsan/kmsan_instr.c:116 pskb_expand_head+0x38b/0x1b00 net/core/skbuff.c:1637 __skb_pad+0x47f/0x900 net/core/skbuff.c:1805 __skb_put_padto include/linux/skbuff.h:3193 [inline] skb_put_padto include/linux/skbuff.h:3212 [inline] send_hsr_supervision_frame+0x122d/0x1500 net/hsr/hsr_device.c:310 hsr_announce+0x1e2/0x370 net/hsr/hsr_device.c:341 call_timer_fn+0x218/0x510 kernel/time/timer.c:1404 expire_timers kernel/time/timer.c:1449 [inline] __run_timers+0xcff/0x1210 kernel/time/timer.c:1773 run_timer_softirq+0x2d/0x50 kernel/time/timer.c:1786 __do_softirq+0x311/0x83d kernel/softirq.c:293

Uninit was created at: kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:144 kmsan_internal_alloc_meta_for_pages mm/kmsan/kmsan_shadow.c:307 [inline] kmsan_alloc_page+0x12a/0x310 mm/kmsan/kmsan_shadow.c:336 __alloc_pages_nodemask+0x57f2/0x5f60 mm/page_alloc.c:4800 __alloc_pages include/linux/gfp.h:498 [inline] __alloc_pages_node include/linux/gfp.h:511 [inline] alloc_pages_node include/linux/gfp.h:525 [inline] __page_frag_cache_refill mm/page_alloc.c:4875 [inline] page_frag_alloc+0x3ae/0x910 mm/page_alloc.c:4905 __napi_alloc_skb+0x193/0xa60 net/core/skbuff.c:519 napi_alloc_skb include/linux/skbuff.h:2825 [inline] page_to_skb+0x19f/0x1100 drivers/net/virtio_net.c:384 receive_mergeable drivers/net/virtio_net.c:924 [inline] receive_buf+0xe57/0x8ac0 drivers/net/virtio_net.c:1033 virtnet_receive drivers/net/virtio_net.c:1323 [inline] virtnet_poll+0x64b/0x19f0 drivers/net/virtio_net.c:1428 napi_poll net/core/dev.c:6532 [inline] net_rx_action+0x786/0x1ab0 net/core/dev.c:6600 __do_softirq+0x311/0x83d kernel/softirq.c:293 =====================================================

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