linux-kernel - Re: [PATCH] fs: fix d_path() with zero-length input buffer

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Date:	Wed, 5 Feb 2014 18:42:45 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
	Jan Kratochvil <jan.kratochvil@...hat.com>,
	Amerigo Wang <amwang@...hat.com>,
	"Jonathan M. Foote" <jmfoote@...t.org>,
	Roland McGrath <roland@...k.frob.com>,
	Pedro Alves <palves@...hat.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH] fs: fix d_path() with zero-length input buffer

On 02/05, Denys Vlasenko wrote:
>
> In prepend_name(), *buflen < dlen + 1 comparison is buggy
> because dlen has unsigned data type, and we can reach this location
> with *buflen == -1.

because, say, path_with_deleted() doesn't check the result of
prepend(), and prepend() updates *buflen unconditionally. I am
wondering if it should be changed too just for consistency.

> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -2833,7 +2833,7 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
>  	u32 dlen = ACCESS_ONCE(name->len);
>  	char *p;
>
> -	if (*buflen < dlen + 1)
> +	if (*buflen < (int)dlen + 1)

perhaps it would be better to simply make dlen "int" ?

Oleg.

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