linux-kernel - Re: [PATCH v2] infiniband: remove WARN that is not kernel bug

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Date:   Mon, 21 Nov 2016 11:25:36 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Dmitry Vyukov <dvyukov@...gle.com>
cc:     jgunthorpe@...idianresearch.com, Valdis.Kletnieks@...edu,
        dledford@...hat.com, sean.hefty@...el.com,
        hal.rosenstock@...il.com, leon@...nel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller@...glegroups.com
Subject: Re: [PATCH v2] infiniband: remove WARN that is not kernel bug

On Mon, 21 Nov 2016, Dmitry Vyukov wrote:

> WARNINGs mean kernel bugs.
> The one in ucma_write() points to user programming error
> or a malicious attempt. This is not a kernel bug, remove it.
> 
> BUG/WARNs that are not kernel bugs hinder automated testing effots.
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Doug Ledford <dledford@...hat.com>
> Cc: Sean Hefty <sean.hefty@...el.com>
> Cc: Hal Rosenstock <hal.rosenstock@...il.com>
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: linux-rdma@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: syzkaller@...glegroups.com
> 
> ---
> Changes since v1:
>  - added printk_once
> ---
>  drivers/infiniband/core/ucma.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
> index 9520154..405d0ce 100644
> --- a/drivers/infiniband/core/ucma.c
> +++ b/drivers/infiniband/core/ucma.c
> @@ -1584,8 +1584,11 @@ static ssize_t ucma_write(struct file *filp, const char __user *buf,
>  	struct rdma_ucm_cmd_hdr hdr;
>  	ssize_t ret;
>  
> -	if (WARN_ON_ONCE(!ib_safe_file_access(filp)))
> +	if (!ib_safe_file_access(filp)) {
> +		printk_once("ucma_write: process %d (%s) tried to do something hinky\n",
> +			task_tgid_vnr(current), current->comm);
>  		return -EACCES;
> +	}
>  
>  	if (len < sizeof(hdr))
>  		return -EINVAL;

FWIW, WARN_ON_ONCE came with commit e6bd18f57aad ("IB/security: Restrict 
use of the write() interface"). Would it make sense to change the other 
places as well?

Regards,
Miroslav