Re: [RFC PATCH 2/9] audit,io_uring,io-wq: add some basic audit support to io_uring

[Pavel Begunkov <asml.silence@gmail.com>]

On 5/21/21 10:49 PM, Paul Moore wrote:
> WARNING - This is a work in progress and should not be merged
> anywhere important.  It is almost surely not complete, and while it
> probably compiles it likely hasn't been booted and will do terrible
> things.  You have been warned.
> 
> This patch adds basic auditing to io_uring operations, regardless of
> their context.  This is accomplished by allocating audit_context
> structures for the io-wq worker and io_uring SQPOLL kernel threads
> as well as explicitly auditing the io_uring operations in
> io_issue_sqe().  The io_uring operations are audited using a new
> AUDIT_URINGOP record, an example is shown below:
> 
>   % <TODO - insert AUDIT_URINGOP record example>
> 
> Thanks to Richard Guy Briggs for review and feedback.
> 
> Signed-off-by: Paul Moore <paul@paul-moore.com>
> ---
[...]
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index e481ac8a757a..e9941d1ad8fd 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -78,6 +78,7 @@
>  #include <linux/task_work.h>
>  #include <linux/pagemap.h>
>  #include <linux/io_uring.h>
> +#include <linux/audit.h>
>  
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/io_uring.h>
> @@ -6105,6 +6106,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
>  	if (req->work.creds && req->work.creds != current_cred())
>  		creds = override_creds(req->work.creds);
>  
> +	if (req->opcode < IORING_OP_LAST)

always true at this point

> +		audit_uring_entry(req->opcode);

So, it adds two if's with memory loads (i.e. current->audit_context)
per request in one of the hottest functions here... No way, nack

Maybe, if it's dynamically compiled into like kprobes if it's
_really_ used.

> +
>  	switch (req->opcode) {
>  	case IORING_OP_NOP:
>  		ret = io_nop(req, issue_flags);
> @@ -6211,6 +6215,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
>  		break;
>  	}
>  
> +	if (req->opcode < IORING_OP_LAST)
> +		audit_uring_exit(!ret, ret);
> +
>  	if (creds)
>  		revert_creds(creds);

-- 
Pavel Begunkov