linux-kernel - Re: [PATCH] proc: potential ERR_PTR dereference on proc_fill

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Date:	Sun, 10 Aug 2014 20:25:39 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Daeseok Youn <daeseok.youn@...il.com>
Cc:	akpm@...ux-foundation.org, oleg@...hat.com, eparis@...hat.com,
	rgb@...hat.com, tixxdz@...ndz.org, adobriyan@...il.com,
	bill.c.roberts@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: potential ERR_PTR dereference on proc_fill_cache()

Daeseok Youn <daeseok.youn@...il.com> writes:

> The d_hash_and_lookup() returns NULL or ERR_PTR on lookup
> failure.

Given that the only error condition can come from .d_hash and that proc
does not implement .d_hash if we want to do something with error returns
let's call BUG_ON. aka:

diff --git a/fs/proc/base.c b/fs/proc/base.c
index f50d4be..49bc09c 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1673,7 +1673,7 @@ bool proc_fill_cache(struct file *file, struct dir_context *ctx,
 	ino_t ino;
 
 	child = d_hash_and_lookup(dir, &qname);
+	BUG_ON(IS_ERR(child))
	if (!child) {
 		child = d_alloc(dir, &qname);
 		if (!child)
 			goto end_instantiate;

Or do you see something in d_hash_and_lookup that I am overlooking?

Eric


> Signed-off-by: Daeseok Youn <daeseok.youn@...il.com>
> ---
>  fs/proc/base.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index f50d4be..49bc09c 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1673,7 +1673,7 @@ bool proc_fill_cache(struct file *file, struct dir_context *ctx,
>  	ino_t ino;
>  
>  	child = d_hash_and_lookup(dir, &qname);
> -	if (!child) {
> +	if (IS_ERR_OR_NULL(child)) {
>  		child = d_alloc(dir, &qname);
>  		if (!child)
>  			goto end_instantiate;
--
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