2010-05-04 12:09:26

by Johannes Weiner

[permalink] [raw]
Subject: [patch] sunrpc: add missing return statement

f300bab "nfsd41: sunrpc: add new xprt class for nfsv4.1 backchannel"
introduced an error case branch that lacks an actual `return' keyword
before the return value. Add it.

Signed-off-by: Johannes Weiner <[email protected]>
Cc: Alexandros Batsakis <[email protected]>
---
net/sunrpc/xprtsock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2444,7 +2444,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(
struct svc_sock *bc_sock;

if (!args->bc_xprt)
- ERR_PTR(-EINVAL);
+ return ERR_PTR(-EINVAL);

xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries);
if (IS_ERR(xprt))


2010-05-04 12:27:22

by Trond Myklebust

[permalink] [raw]
Subject: Re: [patch] sunrpc: add missing return statement

On Tue, 2010-05-04 at 13:59 +0200, Johannes Weiner wrote:
> f300bab "nfsd41: sunrpc: add new xprt class for nfsv4.1 backchannel"
> introduced an error case branch that lacks an actual `return' keyword
> before the return value. Add it.
>
> Signed-off-by: Johannes Weiner <[email protected]>
> Cc: Alexandros Batsakis <[email protected]>
> ---
> net/sunrpc/xprtsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -2444,7 +2444,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(
> struct svc_sock *bc_sock;
>
> if (!args->bc_xprt)
> - ERR_PTR(-EINVAL);
> + return ERR_PTR(-EINVAL);
>
> xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries);
> if (IS_ERR(xprt))

No. It should either be a BUG_ON(), or else be removed entirely.
Returning an error value for something that is clearly a programming bug
is not a particularly useful exercise...

Cheers
Trond

2010-05-04 13:03:09

by Tetsuo Handa

[permalink] [raw]
Subject: Re: [patch] sunrpc: add missing return statement

Trond Myklebust wrote:
> On Tue, 2010-05-04 at 13:59 +0200, Johannes Weiner wrote:
> > f300bab "nfsd41: sunrpc: add new xprt class for nfsv4.1 backchannel"
> > introduced an error case branch that lacks an actual `return' keyword
> > before the return value. Add it.
> >
> > Signed-off-by: Johannes Weiner <[email protected]>
> > Cc: Alexandros Batsakis <[email protected]>
> > ---
> > net/sunrpc/xprtsock.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- a/net/sunrpc/xprtsock.c
> > +++ b/net/sunrpc/xprtsock.c
> > @@ -2444,7 +2444,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(
> > struct svc_sock *bc_sock;
> >
> > if (!args->bc_xprt)
> > - ERR_PTR(-EINVAL);
> > + return ERR_PTR(-EINVAL);
> >
> > xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries);
> > if (IS_ERR(xprt))
>
> No. It should either be a BUG_ON(), or else be removed entirely.
> Returning an error value for something that is clearly a programming bug
> is not a particularly useful exercise...
>
Removing NULL check is wrong because it will NULL pointer dereference later.

Tetsuo Handa wrote:
> Jani Nikula wrote:
> > Signed-off-by: Jani Nikula <[email protected]>
> >
> > ---
> >
> > NOTE: I'm afraid I'm unable to test this; please consider this more a
> > bug report than a complete patch.
> > ---
> Indeed, it has to be "return ERR_PTR(-EINVAL);".
> Otherwise, it will trigger NULL pointer dereference some lines later.
>
> bc_sock = container_of(args->bc_xprt, struct svc_sock, sk_xprt);
> bc_sock->sk_bc_xprt = xprt;
>
> This bug was introduced by f300baba5a1536070d6d77bf0c8c4ca999bb4f0f
> "nfsd41: sunrpc: add new xprt class for nfsv4.1 backchannel" and
> exists in 2.6.32 and later.

2010-05-04 13:13:35

by Trond Myklebust

[permalink] [raw]
Subject: Re: [patch] sunrpc: add missing return statement

On Tue, 2010-05-04 at 22:03 +0900, Tetsuo Handa wrote:
> Trond Myklebust wrote:
> > On Tue, 2010-05-04 at 13:59 +0200, Johannes Weiner wrote:
> > > f300bab "nfsd41: sunrpc: add new xprt class for nfsv4.1 backchannel"
> > > introduced an error case branch that lacks an actual `return' keyword
> > > before the return value. Add it.
> > >
> > > Signed-off-by: Johannes Weiner <[email protected]>
> > > Cc: Alexandros Batsakis <[email protected]>
> > > ---
> > > net/sunrpc/xprtsock.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > --- a/net/sunrpc/xprtsock.c
> > > +++ b/net/sunrpc/xprtsock.c
> > > @@ -2444,7 +2444,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(
> > > struct svc_sock *bc_sock;
> > >
> > > if (!args->bc_xprt)
> > > - ERR_PTR(-EINVAL);
> > > + return ERR_PTR(-EINVAL);
> > >
> > > xprt = xs_setup_xprt(args, xprt_tcp_slot_table_entries);
> > > if (IS_ERR(xprt))
> >
> > No. It should either be a BUG_ON(), or else be removed entirely.
> > Returning an error value for something that is clearly a programming bug
> > is not a particularly useful exercise...
> >
> Removing NULL check is wrong because it will NULL pointer dereference later.

Wrong. Removing NULL check is _right_ because calling this function
without setting up a back channel first is a major BUG. Returning an
error value to the user is pointless, since the user has no control over
this. It is entirely under control of the sunrpc developers...

Trond


2010-05-04 14:02:28

by Tetsuo Handa

[permalink] [raw]
Subject: Re: [patch] sunrpc: add missing return statement

Trond Myklebust wrote:
> > > No. It should either be a BUG_ON(), or else be removed entirely.
> > > Returning an error value for something that is clearly a programming bug
> > > is not a particularly useful exercise...
> > >
> > Removing NULL check is wrong because it will NULL pointer dereference later.
>
> Wrong. Removing NULL check is _right_ because calling this function
> without setting up a back channel first is a major BUG. Returning an
> error value to the user is pointless, since the user has no control over
> this. It is entirely under control of the sunrpc developers...
>
For security people, removing

if (!args->bc_xprt)
ERR_PTR(-EINVAL);

is worse and changing to

BUG_ON(!args->bc_xprt);

is better.