Re: [PATCH net] nbd: always initialize struct msghdr completely

[Simon Horman]

On Fri, Jan 12, 2024 at 01:26:57PM +0000, Eric Dumazet wrote:
> syzbot complains that msg->msg_get_inq value can be uninitialized [1]
> 
> struct msghdr got many new fields recently, we should always make
> sure their values is zero by default.
> 
> [1]
>  BUG: KMSAN: uninit-value in tcp_recvmsg+0x686/0xac0 net/ipv4/tcp.c:2571
>   tcp_recvmsg+0x686/0xac0 net/ipv4/tcp.c:2571
>   inet_recvmsg+0x131/0x580 net/ipv4/af_inet.c:879
>   sock_recvmsg_nosec net/socket.c:1044 [inline]
>   sock_recvmsg+0x12b/0x1e0 net/socket.c:1066
>   __sock_xmit+0x236/0x5c0 drivers/block/nbd.c:538
>   nbd_read_reply drivers/block/nbd.c:732 [inline]
>   recv_work+0x262/0x3100 drivers/block/nbd.c:863
>   process_one_work kernel/workqueue.c:2627 [inline]
>   process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2700
>   worker_thread+0xf45/0x1490 kernel/workqueue.c:2781
>   kthread+0x3ed/0x540 kernel/kthread.c:388
>   ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
>   ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
> 
> Local variable msg created at:
>   __sock_xmit+0x4c/0x5c0 drivers/block/nbd.c:513
>   nbd_read_reply drivers/block/nbd.c:732 [inline]
>   recv_work+0x262/0x3100 drivers/block/nbd.c:863
> 
> CPU: 1 PID: 7465 Comm: kworker/u5:1 Not tainted 6.7.0-rc7-syzkaller-00041-gf016f7547aee #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> Workqueue: nbd5-recv recv_work
> 
> Fixes: f94fd25cb0aa ("tcp: pass back data left in socket after receive")
> Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>

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