Re: [PATCH 5.10 042/103] net/rds: Avoid potential use after free in rds_send_remove_from_sock

[Greg Kroah-Hartman]

On Mon, Apr 19, 2021 at 03:05:53PM +0200, Greg Kroah-Hartman wrote:
> From: Aditya Pakki <pakki001@xxxxxxx>
> 
> [ Upstream commit 0c85a7e87465f2d4cbc768e245f4f45b2f299b05 ]
> 
> In case of rs failure in rds_send_remove_from_sock(), the 'rm' resource
> is freed and later under spinlock, causing potential use-after-free.
> Set the free pointer to NULL to avoid undefined behavior.
> 
> Signed-off-by: Aditya Pakki <pakki001@xxxxxxx>
> Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>  net/rds/message.c | 1 +
>  net/rds/send.c    | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/rds/message.c b/net/rds/message.c
> index 799034e0f513..4fc66ff0f1ec 100644
> --- a/net/rds/message.c
> +++ b/net/rds/message.c
> @@ -180,6 +180,7 @@ void rds_message_put(struct rds_message *rm)
>  		rds_message_purge(rm);
>  
>  		kfree(rm);
> +		rm = NULL;
>  	}
>  }
>  EXPORT_SYMBOL_GPL(rds_message_put);
> diff --git a/net/rds/send.c b/net/rds/send.c
> index 985d0b7713ac..fe5264b9d4b3 100644
> --- a/net/rds/send.c
> +++ b/net/rds/send.c
> @@ -665,7 +665,7 @@ static void rds_send_remove_from_sock(struct list_head *messages, int status)
>  unlock_and_drop:
>  		spin_unlock_irqrestore(&rm->m_rs_lock, flags);
>  		rds_message_put(rm);
> -		if (was_on_sock)
> +		if (was_on_sock && rm)
>  			rds_message_put(rm);
>  	}
>  
> -- 
> 2.30.2
> 
> 
> 

Ah crap, I will go drop this stuff.

I also will strongly recommend that all maintainers blacklist umn.edu
patches at this point in time, as it is obvious that a professor there
is operating a sociological experiment on Linux kernel maintainers and
is wasting our time.

This is not ok.

greg k-h