linux-kernel - Re: [PATCH] swapfile: fix name leak in swapoff

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Date:	Wed, 14 Nov 2012 11:59:45 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Xiaotian Feng <xtfeng@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Xiaotian Feng <dannyfeng@...cent.com>,
	Jeff Layton <jlayton@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] swapfile: fix name leak in swapoff

On Thu,  1 Nov 2012 17:36:55 +0800
Xiaotian Feng <xtfeng@...il.com> wrote:

> there's a name leak introduced by commit 91a27b2, add the missing
> putname.
> 
> Signed-off-by: Xiaotian Feng <dannyfeng@...cent.com>
> Cc: Jeff Layton <jlayton@...hat.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> ---
>  mm/swapfile.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 71cd288..459fe30 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1608,6 +1608,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
>  out_dput:
>  	filp_close(victim, NULL);
>  out:
> +	if (pathname && !IS_ERR(pathname))
> +		putname(pathname);
>  	return err;
>  }

This way is simpler:

--- a/mm/swapfile.c~swapfile-fix-name-leak-in-swapoff-fix
+++ a/mm/swapfile.c
@@ -1507,9 +1507,8 @@ SYSCALL_DEFINE1(swapoff, const char __us
 	BUG_ON(!current->mm);
 
 	pathname = getname(specialfile);
-	err = PTR_ERR(pathname);
 	if (IS_ERR(pathname))
-		goto out;
+		return PTR_ERR(pathname);
 
 	victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
 	err = PTR_ERR(victim);
@@ -1615,8 +1614,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
 out_dput:
 	filp_close(victim, NULL);
 out:
-	if (pathname && !IS_ERR(pathname))
-		putname(pathname);
+	putname(pathname);
 	return err;
 }
 
_


It would be even simpler to do the putname() immediately after
file_open_name(), but it is nice to keep `pathname' live for the whole
function in case it gets used by later code.

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