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

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Date:	Mon, 11 Aug 2014 14:43:37 +0900
From:	DaeSeok Youn <daeseok.youn@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, oleg <oleg@...hat.com>,
	eparis@...hat.com, rgb@...hat.com, tixxdz@...ndz.org,
	adobriyan@...il.com, bill.c.roberts@...il.com,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] proc: potential ERR_PTR dereference on proc_fill_cache()

2014-08-11 12:25 GMT+09:00 Eric W. Biederman <ebiederm@...ssion.com>:
> 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:
Yes, you're right. proc doesn't implement .d_hash, so my patch is not needed.
It couldn't return ERR_PTR(-error) without implementing .d_hash
This patch should be dropped.

>
> 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?
No.. I should check more carefully. sorry for that.

Thanks for review.

regards,
Daeseok Youn.

>
> 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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