[PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[Dan Carpenter]

We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
is expecting error pointers so it results in a NULL dereference.

Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
Signed-off-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>

diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
index 48332a6ed738..74a66cc162ed 100644
--- a/net/rds/ib_frmr.c
+++ b/net/rds/ib_frmr.c
@@ -38,7 +38,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
 	struct rds_ib_mr_pool *pool;
 	struct rds_ib_mr *ibmr = NULL;
 	struct rds_ib_frmr *frmr;
-	int err = 0;
+	int err;
 
 	if (npages <= RDS_MR_8K_MSG_SIZE)
 		pool = rds_ibdev->mr_8k_pool;
@@ -61,6 +61,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
 			 pool->fmr_attr.max_pages);
 	if (IS_ERR(frmr->mr)) {
 		pr_warn("RDS/IB: %s failed to allocate MR", __func__);
+		err = -ENOMEM;
 		goto out_no_cigar;
 	}
 
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Re: [PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[Yuval Shaia]

On Wed, Jun 14, 2017 at 01:39:24PM +0300, Dan Carpenter wrote:
> We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
> is expecting error pointers so it results in a NULL dereference.
> 
> Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
> Signed-off-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> 
> diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
> index 48332a6ed738..74a66cc162ed 100644
> --- a/net/rds/ib_frmr.c
> +++ b/net/rds/ib_frmr.c
> @@ -38,7 +38,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
>  	struct rds_ib_mr_pool *pool;
>  	struct rds_ib_mr *ibmr = NULL;
>  	struct rds_ib_frmr *frmr;
> -	int err = 0;
> +	int err;

Can we trust it'll be zero?

>  
>  	if (npages <= RDS_MR_8K_MSG_SIZE)
>  		pool = rds_ibdev->mr_8k_pool;
> @@ -61,6 +61,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
>  			 pool->fmr_attr.max_pages);
>  	if (IS_ERR(frmr->mr)) {
>  		pr_warn("RDS/IB: %s failed to allocate MR", __func__);
> +		err = -ENOMEM;
>  		goto out_no_cigar;
>  	}
>  
> --
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Re: [PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[Dan Carpenter]

On Wed, Jun 14, 2017 at 03:54:24PM +0300, Yuval Shaia wrote:
> On Wed, Jun 14, 2017 at 01:39:24PM +0300, Dan Carpenter wrote:
> > We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
> > is expecting error pointers so it results in a NULL dereference.
> > 
> > Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
> > Signed-off-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> > 
> > diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
> > index 48332a6ed738..74a66cc162ed 100644
> > --- a/net/rds/ib_frmr.c
> > +++ b/net/rds/ib_frmr.c
> > @@ -38,7 +38,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
> >  	struct rds_ib_mr_pool *pool;
> >  	struct rds_ib_mr *ibmr = NULL;
> >  	struct rds_ib_frmr *frmr;
> > -	int err = 0;
> > +	int err;
> 
> Can we trust it'll be zero?

We don't ever want it to be zero.  This way, hopefully, GCC will catch
it if we introduce any new bugs where we forget to set it to negative.

regards,
dan carpenter

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Re: [PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[Yuval Shaia]

On Wed, Jun 14, 2017 at 04:03:40PM +0300, Dan Carpenter wrote:
> On Wed, Jun 14, 2017 at 03:54:24PM +0300, Yuval Shaia wrote:
> > On Wed, Jun 14, 2017 at 01:39:24PM +0300, Dan Carpenter wrote:
> > > We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
> > > is expecting error pointers so it results in a NULL dereference.
> > > 
> > > Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > 
> > > diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
> > > index 48332a6ed738..74a66cc162ed 100644
> > > --- a/net/rds/ib_frmr.c
> > > +++ b/net/rds/ib_frmr.c
> > > @@ -38,7 +38,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
> > >  	struct rds_ib_mr_pool *pool;
> > >  	struct rds_ib_mr *ibmr = NULL;
> > >  	struct rds_ib_frmr *frmr;
> > > -	int err = 0;
> > > +	int err;
> > 
> > Can we trust it'll be zero?
> 
> We don't ever want it to be zero.  This way, hopefully, GCC will catch
> it if we introduce any new bugs where we forget to set it to negative.

I see your point, in a "good" case we just return the ptr.

Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>

> 
> regards,
> dan carpenter
> 

Re: [PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[Julia Lawall]

On Wed, 14 Jun 2017, Yuval Shaia wrote:

> On Wed, Jun 14, 2017 at 01:39:24PM +0300, Dan Carpenter wrote:
> > We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
> > is expecting error pointers so it results in a NULL dereference.
> >
> > Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
> > Signed-off-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> >
> > diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
> > index 48332a6ed738..74a66cc162ed 100644
> > --- a/net/rds/ib_frmr.c
> > +++ b/net/rds/ib_frmr.c
> > @@ -38,7 +38,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
> >  	struct rds_ib_mr_pool *pool;
> >  	struct rds_ib_mr *ibmr = NULL;
> >  	struct rds_ib_frmr *frmr;
> > -	int err = 0;
> > +	int err;
>
> Can we trust it'll be zero?

No need.  With the change below there is always an assignment before the
only reference at the end of the function.

julia

>
> >
> >  	if (npages <= RDS_MR_8K_MSG_SIZE)
> >  		pool = rds_ibdev->mr_8k_pool;
> > @@ -61,6 +61,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
> >  			 pool->fmr_attr.max_pages);
> >  	if (IS_ERR(frmr->mr)) {
> >  		pr_warn("RDS/IB: %s failed to allocate MR", __func__);
> > +		err = -ENOMEM;
> >  		goto out_no_cigar;
> >  	}
> >
> > --
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Re: [PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[santosh.shilimkar]

On 6/14/17 3:39 AM, Dan Carpenter wrote:
> We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
> is expecting error pointers so it results in a NULL dereference.
>
> Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
Thanks Dan for fix.

Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

You haven't copied netdev. Can you please resend the patch
with my ack on netdev so that Dave can pick it up.

Re: [PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[Avinash Repaka]

Reviewed-by: Avinash Repaka <avinash.repaka@oracle.com>

On 06/14/2017 03:39 AM, Dan Carpenter wrote:
> We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
> is expecting error pointers so it results in a NULL dereference.
>
> Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
> index 48332a6ed738..74a66cc162ed 100644
> --- a/net/rds/ib_frmr.c
> +++ b/net/rds/ib_frmr.c
> @@ -38,7 +38,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
>   	struct rds_ib_mr_pool *pool;
>   	struct rds_ib_mr *ibmr = NULL;
>   	struct rds_ib_frmr *frmr;
> -	int err = 0;
> +	int err;
>   
>   	if (npages <= RDS_MR_8K_MSG_SIZE)
>   		pool = rds_ibdev->mr_8k_pool;
> @@ -61,6 +61,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
>   			 pool->fmr_attr.max_pages);
>   	if (IS_ERR(frmr->mr)) {
>   		pr_warn("RDS/IB: %s failed to allocate MR", __func__);
> +		err = -ENOMEM;
>   		goto out_no_cigar;
>   	}
>