Re: KMSAN: uninit-value in kernel_sendmsg

[Dmitry Vyukov]

On Fri, Nov 8, 2019 at 4:54 PM syzbot
<syzbot+4b6f070bb7a8ea5420d4@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> 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: syzbot+4b6f070bb7a8ea5420d4@xxxxxxxxxxxxxxxxxxxxxxxxx

I think this is:

#syz dup: KMSAN: use-after-free in rxrpc_send_keepalive

https://syzkaller.appspot.com/bug?id=428e72dc175d0f4b23a1fb9b7d3d16fad7ef2a4b

> =====================================================
> 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
> =====================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
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>
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