Re: [tipc-discussion] [PATCH] tipc: switch order of device registration to fix a crash

[David M. <da...@da...>]

From: hujunwei <huj...@hu...>
Date: Thu, 16 May 2019 10:51:15 +0800

> From: Junwei Hu <huj...@hu...>
> 
> When tipc is loaded while many processes try to create a TIPC socket,
> a crash occurs:
>  PANIC: Unable to handle kernel paging request at virtual
>  address "dfff20000000021d"
>  pc : tipc_sk_create+0x374/0x1180 [tipc]
>  lr : tipc_sk_create+0x374/0x1180 [tipc]
>    Exception class = DABT (current EL), IL = 32 bits
>  Call trace:
>   tipc_sk_create+0x374/0x1180 [tipc]
>   __sock_create+0x1cc/0x408
>   __sys_socket+0xec/0x1f0
>   __arm64_sys_socket+0x74/0xa8
>  ...
> 
> This is due to race between sock_create and unfinished
> register_pernet_device. tipc_sk_insert tries to do
> "net_generic(net, tipc_net_id)".
> but tipc_net_id is not initialized yet.
> 
> So switch the order of the two to close the race.
> 
> This can be reproduced with multiple processes doing socket(AF_TIPC, ...)
> and one process doing module removal.
> 
> Fixes: a62fbccecd62 ("tipc: make subscriber server support net namespace")
> Signed-off-by: Junwei Hu <huj...@hu...>
> Reported-by: Wang Wang <wan...@hu...>
> Reviewed-by: Xiaogang Wang <wan...@hu...>

Applied and queued up for -stable.