linux-kernel - Re: [PATCH 1/6] ERR_PTR: if errno value is known at compile time, make sure it's valid

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Date:	Mon, 19 May 2008 10:38:52 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Marcin Slusarz <marcin.slusarz@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	Christoph Hellwig <hch@....de>, tom@...ngridcomputing.com
Subject: Re: [PATCH 1/6] ERR_PTR: if errno value is known at compile time,
	make sure it's valid

On Sun, May 18, 2008 at 11:56:53PM +0200, Marcin Slusarz wrote:
> ERR_PTR is easy to call with wrong argument (positive errno),
> and this error lead to catastrophic event - oops or kernel panic
> (dereference of invalid pointer).
> 
> As most of error handling code paths are rarely tested, this kind of
> bug can be hidden for years.
> 
> (Currently there are > 1400 calls of ERR_PTR with constant argument.)

> --- a/include/linux/err.h
> +++ b/include/linux/err.h
> @@ -19,11 +19,13 @@
>  
>  #define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
>  
> -static inline void *ERR_PTR(long error)
> +static inline void *__ERR_PTR(long error)
>  {
>  	return (void *) error;
>  }
>  
> +#define ERR_PTR(error) (BUILD_BUG_ON(__builtin_constant_p(error) && !IS_ERR_VALUE(error)), __ERR_PTR(error))

This needs comment that this construct must be a macro, otherwise gcc
does something stupid and doesn't break the build (at least in the case
below). BTW, I used grep(1) to find it.


[PATCH] xprtrdma: fix ERR_PTR(E typo

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -661,7 +661,7 @@ static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
 
 	cma_xprt = rdma_create_xprt(serv, 1);
 	if (!cma_xprt)
-		return ERR_PTR(ENOMEM);
+		return ERR_PTR(-ENOMEM);
 	xprt = &cma_xprt->sc_xprt;
 
 	listen_id = rdma_create_id(rdma_listen_handler, cma_xprt, RDMA_PS_TCP);

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