[PATCH] staging: kpc2000: replace assertion with recovery code

[PATCH] staging: kpc2000: replace assertion with recovery code

[Aditya Pakki]

In kpc_dma_transfer, if either priv or ldev is NULL, crashing the
process is excessive and is not needed. Instead of asserting, by
passing the error upstream, the error can be handled.

Signed-off-by: Aditya Pakki <pakki001@umn.edu>
---
 drivers/staging/kpc2000/kpc_dma/fileops.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c
index cb52bd9a6d2f..1c4633267cc1 100644
--- a/drivers/staging/kpc2000/kpc_dma/fileops.c
+++ b/drivers/staging/kpc2000/kpc_dma/fileops.c
@@ -49,9 +49,11 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
 	u64 dma_addr;
 	u64 user_ctl;
 
-	BUG_ON(priv == NULL);
+	if (!priv)
+		return -EINVAL;
 	ldev = priv->ldev;
-	BUG_ON(ldev == NULL);
+	if (!ldev)
+		return -EINVAL;
 
 	acd = kzalloc(sizeof(*acd), GFP_KERNEL);
 	if (!acd) {
-- 
2.20.1

Re: [PATCH] staging: kpc2000: replace assertion with recovery code

[Greg Kroah-Hartman]

On Sun, Dec 15, 2019 at 12:12:37PM -0600, Aditya Pakki wrote:
> In kpc_dma_transfer, if either priv or ldev is NULL, crashing the
> process is excessive and is not needed. Instead of asserting, by
> passing the error upstream, the error can be handled.
> 
> Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> ---
>  drivers/staging/kpc2000/kpc_dma/fileops.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c
> index cb52bd9a6d2f..1c4633267cc1 100644
> --- a/drivers/staging/kpc2000/kpc_dma/fileops.c
> +++ b/drivers/staging/kpc2000/kpc_dma/fileops.c
> @@ -49,9 +49,11 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
>  	u64 dma_addr;
>  	u64 user_ctl;
>  
> -	BUG_ON(priv == NULL);
> +	if (!priv)
> +		return -EINVAL;

How can prive ever be NULL here?  Can you track back to all callers to
verify this?  If so, just remove the check.

thanks,

greg k-h

Re: [PATCH] staging: kpc2000: replace assertion with recovery code

[Dan Carpenter]

On Sun, Dec 15, 2019 at 07:28:14PM +0100, Greg Kroah-Hartman wrote:
> On Sun, Dec 15, 2019 at 12:12:37PM -0600, Aditya Pakki wrote:
> > In kpc_dma_transfer, if either priv or ldev is NULL, crashing the
> > process is excessive and is not needed. Instead of asserting, by
> > passing the error upstream, the error can be handled.
> > 
> > Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> > ---
> >  drivers/staging/kpc2000/kpc_dma/fileops.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c
> > index cb52bd9a6d2f..1c4633267cc1 100644
> > --- a/drivers/staging/kpc2000/kpc_dma/fileops.c
> > +++ b/drivers/staging/kpc2000/kpc_dma/fileops.c
> > @@ -49,9 +49,11 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
> >  	u64 dma_addr;
> >  	u64 user_ctl;
> >  
> > -	BUG_ON(priv == NULL);
> > +	if (!priv)
> > +		return -EINVAL;
> 
> How can prive ever be NULL here?  Can you track back to all callers to
> verify this?  If so, just remove the check.
> 

Smatch says that "priv" can't be NULL.

Also if you have a NULL dereference the kernel prints a nice stack
trace.  Normally just doing the NULL dereference and Oopsing is better
than doing a BUG_ON().  The one exception would be when the Oops leads
to filesystem corruption.

regards,
dan carpenter