KMSAN: uninit-value in ieee80211_skb_resize

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c5a13b33 kmsan: clang-format core
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1366df53900000
kernel config: https://syzkaller.appspot.com/x/.config?x=20f149ad694ba4be
dashboard link: https://syzkaller.appspot.com/bug?extid=32fd1a1bfe355e93f1e2
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14e95cd3900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11abf481900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+32fd1a...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in ieee80211_skb_resize+0x8c0/0x980 net/mac80211/tx.c:1955
CPU: 0 PID: 8539 Comm: syz-executor053 Not tainted 5.9.0-rc4-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+0x21c/0x280 lib/dump_stack.c:118
kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:122
__msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:219
ieee80211_skb_resize+0x8c0/0x980 net/mac80211/tx.c:1955
ieee80211_build_hdr+0x2939/0x41f0 net/mac80211/tx.c:2825
__ieee80211_subif_start_xmit+0x172a/0x7300 net/mac80211/tx.c:3999
ieee80211_subif_start_xmit+0x14b/0x19a0 net/mac80211/tx.c:4144
__netdev_start_xmit include/linux/netdevice.h:4634 [inline]
netdev_start_xmit include/linux/netdevice.h:4648 [inline]
xmit_one+0x3cf/0x750 net/core/dev.c:3561
dev_hard_start_xmit+0x196/0x420 net/core/dev.c:3577
sch_direct_xmit+0x5d3/0x1a50 net/sched/sch_generic.c:314
qdisc_restart net/sched/sch_generic.c:377 [inline]
__qdisc_run+0x35b/0x490 net/sched/sch_generic.c:385
qdisc_run include/net/pkt_sched.h:134 [inline]
__dev_xmit_skb net/core/dev.c:3752 [inline]
__dev_queue_xmit+0x2cfa/0x4470 net/core/dev.c:4105
dev_queue_xmit+0x4b/0x60 net/core/dev.c:4169
packet_snd net/packet/af_packet.c:2989 [inline]
packet_sendmsg+0x8542/0x9a80 net/packet/af_packet.c:3014
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
__sys_sendto+0x9dc/0xc80 net/socket.c:1992
__do_sys_sendto net/socket.c:2004 [inline]
__se_sys_sendto+0x107/0x130 net/socket.c:2000
__x64_sys_sendto+0x6e/0x90 net/socket.c:2000
do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x441ea9
Code: e8 bc 00 03 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffc4414388 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441ea9
RDX: 000000000000000e RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000004800 R11: 0000000000000246 R12: 0000000000000032
R13: 0000000000000000 R14: 000000000000000c R15: 0000000000000004

Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:143 [inline]
kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:126
kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:80
slab_alloc_node mm/slub.c:2907 [inline]
__kmalloc_node_track_caller+0x9aa/0x12f0 mm/slub.c:4511
__kmalloc_reserve net/core/skbuff.c:142 [inline]
__alloc_skb+0x35f/0xb30 net/core/skbuff.c:210
alloc_skb include/linux/skbuff.h:1094 [inline]
alloc_skb_with_frags+0x1f2/0xc10 net/core/skbuff.c:5771
sock_alloc_send_pskb+0xc83/0xe50 net/core/sock.c:2348
packet_alloc_skb net/packet/af_packet.c:2837 [inline]
packet_snd net/packet/af_packet.c:2932 [inline]
packet_sendmsg+0x6abb/0x9a80 net/packet/af_packet.c:3014
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
__sys_sendto+0x9dc/0xc80 net/socket.c:1992
__do_sys_sendto net/socket.c:2004 [inline]
__se_sys_sendto+0x107/0x130 net/socket.c:2000
__x64_sys_sendto+0x6e/0x90 net/socket.c:2000
do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================


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