KMSAN: uninit-value in batadv_bla_tx

[syzbot]

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@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
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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