Subject: KMSAN: uninit-value in kernel_sendmsg

From: syzbot <[email-masked]>
Date: Fri, 08 Nov 2019 07:54:09 -0800

Hello,

syzbot found the following crash on:

HEAD commit:    124037e0 kmsan: drop inlines, rename do_kmsan_task_create()
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1648eb9d600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f03c659d0830ab8d
dashboard link: https://syzkaller.appspot.com/bug?extid=4b6f070bb7a8ea5420d4
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

=====================================================
BUG: KMSAN: uninit-value in rxrpc_send_keepalive+0x2fa/0x830  
net/rxrpc/output.c:655
CPU: 0 PID: 3367 Comm: kworker/0:2 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: krxrpcd rxrpc_peer_keepalive_worker
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x191/0x1f0 lib/dump_stack.c:113
  kmsan_report+0x13a/0x2b0 mm/kmsan/kmsan_report.c:108
  __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
  sock_sendmsg_nosec net/socket.c:637 [inline]
  sock_sendmsg net/socket.c:657 [inline]
  kernel_sendmsg+0x2c9/0x440 net/socket.c:677
  rxrpc_send_keepalive+0x2fa/0x830 net/rxrpc/output.c:655
  rxrpc_peer_keepalive_dispatch net/rxrpc/peer_event.c:369 [inline]
  rxrpc_peer_keepalive_worker+0xb82/0x1510 net/rxrpc/peer_event.c:430
  process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
  worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
  kthread+0x4b5/0x4f0 kernel/kthread.c:256
  ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Uninit was created at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:150 [inline]
  kmsan_internal_poison_shadow+0x53/0x100 mm/kmsan/kmsan.c:134
  kmsan_slab_alloc+0xaa/0x120 mm/kmsan/kmsan_hooks.c:103
  slab_alloc_node mm/slub.c:2790 [inline]
  slab_alloc mm/slub.c:2799 [inline]
  kmem_cache_alloc_trace+0x8c5/0xd20 mm/slub.c:2816
  kmalloc include/linux/slab.h:552 [inline]
  __hw_addr_create_ex net/core/dev_addr_lists.c:30 [inline]
  __hw_addr_add_ex net/core/dev_addr_lists.c:76 [inline]
  __hw_addr_add net/core/dev_addr_lists.c:84 [inline]
  dev_addr_init+0x152/0x700 net/core/dev_addr_lists.c:464
  alloc_netdev_mqs+0x2a9/0x1650 net/core/dev.c:9150
  rtnl_create_link+0x559/0x1190 net/core/rtnetlink.c:2931
  __rtnl_newlink net/core/rtnetlink.c:3186 [inline]
  rtnl_newlink+0x2757/0x38d0 net/core/rtnetlink.c:3254
  rtnetlink_rcv_msg+0x115a/0x1580 net/core/rtnetlink.c:5223
  netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
  rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5241
  netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
  netlink_unicast+0xf6c/0x1050 net/netlink/af_netlink.c:1328
  netlink_sendmsg+0x110f/0x1330 net/netlink/af_netlink.c:1917
  sock_sendmsg_nosec net/socket.c:637 [inline]
  sock_sendmsg net/socket.c:657 [inline]
  ___sys_sendmsg+0x14ff/0x1590 net/socket.c:2311
  __sys_sendmsg net/socket.c:2356 [inline]
  __do_sys_sendmsg net/socket.c:2365 [inline]
  __se_sys_sendmsg+0x305/0x460 net/socket.c:2363
  __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2363
  do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
  entry_SYSCALL_64_after_hwframe+0x63/0xe7
=====================================================

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