2022-08-24 08:11:47

by CGEL

Subject: [PATCH] infiniband: remove unnecessary null check

From: Minghao Chi <[email protected]>

container_of is never null, so this null check is
unnecessary.

Reported-by: Zeal Robot <[email protected]>
Signed-off-by: Minghao Chi <[email protected]>
---
drivers/infiniband/sw/rdmavt/vt.c | 2 --
1 file changed, 2 deletions(-)

diff --git a/drivers/infiniband/sw/rdmavt/vt.c b/drivers/infiniband/sw/rdmavt/vt.c
index 59481ae39505..b2d83b4958fc 100644
--- a/drivers/infiniband/sw/rdmavt/vt.c
+++ b/drivers/infiniband/sw/rdmavt/vt.c
@@ -50,8 +50,6 @@ struct rvt_dev_info *rvt_alloc_device(size_t size, int nports)
struct rvt_dev_info *rdi;

rdi = container_of(_ib_alloc_device(size), struct rvt_dev_info, ibdev);
- if (!rdi)
- return rdi;

rdi->ports = kcalloc(nports, sizeof(*rdi->ports), GFP_KERNEL);
if (!rdi->ports)
--
2.25.1

2022-08-24 08:21:56

by Niels Dossche

Subject: Re: [PATCH] infiniband: remove unnecessary null check

On 8/24/22 10:05, [email protected] wrote:
> From: Minghao Chi <[email protected]>
>
> container_of is never null, so this null check is
> unnecessary.
>
> Reported-by: Zeal Robot <[email protected]>
> Signed-off-by: Minghao Chi <[email protected]>
> ---
> drivers/infiniband/sw/rdmavt/vt.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rdmavt/vt.c b/drivers/infiniband/sw/rdmavt/vt.c
> index 59481ae39505..b2d83b4958fc 100644
> --- a/drivers/infiniband/sw/rdmavt/vt.c
> +++ b/drivers/infiniband/sw/rdmavt/vt.c
> @@ -50,8 +50,6 @@ struct rvt_dev_info *rvt_alloc_device(size_t size, int nports)
> struct rvt_dev_info *rdi;
>
> rdi = container_of(_ib_alloc_device(size), struct rvt_dev_info, ibdev);
> - if (!rdi)
> - return rdi;
>
> rdi->ports = kcalloc(nports, sizeof(*rdi->ports), GFP_KERNEL);
> if (!rdi->ports)

I believe this patch is incorrect because "_ib_alloc_device" may return a null pointer.
Note that the first member of "rvt_dev_info" is "ib_device", so the check on container_of effectively checks if the allocation failed, which is necessary to check.

2022-08-24 12:25:12

by Leon Romanovsky

Subject: Re: [PATCH] infiniband: remove unnecessary null check

On Wed, Aug 24, 2022 at 10:15:56AM +0200, Niels Dossche wrote:
> On 8/24/22 10:05, [email protected] wrote:
> > From: Minghao Chi <[email protected]>
> >
> > container_of is never null, so this null check is
> > unnecessary.
> >
> > Reported-by: Zeal Robot <[email protected]>
> > Signed-off-by: Minghao Chi <[email protected]>
> > ---
> > drivers/infiniband/sw/rdmavt/vt.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff --git a/drivers/infiniband/sw/rdmavt/vt.c b/drivers/infiniband/sw/rdmavt/vt.c
> > index 59481ae39505..b2d83b4958fc 100644
> > --- a/drivers/infiniband/sw/rdmavt/vt.c
> > +++ b/drivers/infiniband/sw/rdmavt/vt.c
> > @@ -50,8 +50,6 @@ struct rvt_dev_info *rvt_alloc_device(size_t size, int nports)
> > struct rvt_dev_info *rdi;
> >
> > rdi = container_of(_ib_alloc_device(size), struct rvt_dev_info, ibdev);
> > - if (!rdi)
> > - return rdi;
> >
> > rdi->ports = kcalloc(nports, sizeof(*rdi->ports), GFP_KERNEL);
> > if (!rdi->ports)
>
> I believe this patch is incorrect because "_ib_alloc_device" may return a null pointer.
> Note that the first member of "rvt_dev_info" is "ib_device", so the check on container_of effectively checks if the allocation failed, which is necessary to check.

You are absolutely right, this container_of() and check later are done
on purpose. It is open-coded variant of ib_alloc_device(...) macro.

Thanks