linux-kernel - Re: [EDT] [PATCH] devpts/inode.c : Fix Possible dentry NULL dereference

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Message-ID: <CAFLxGvwAV1duoAmodrUigyhzN-2cAkG2Ae6DXUtWCyOzPHOk7Q@mail.gmail.com>
Date:	Thu, 21 May 2015 12:42:01 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	maninder1.s@...sung.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Fabian Frederick <fabf@...net.be>,
	Al Viro <viro@...iv.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	"v.narang@...sung.com" <v.narang@...sung.com>
Subject: Re: [EDT] [PATCH] devpts/inode.c : Fix Possible dentry NULL dereference

On Thu, May 21, 2015 at 12:28 PM, Maninder Singh
<maninder1.s@...sung.com> wrote:
>
> EP-F6AA0618C49C4AEDA73BFF1B39950BAB

What is this?

> Hi,
>
> Subject: [PATCH 1/1] devpts/inode.c : Fix Possible dentry NULL dereference
>
> Issue reported by static tool Analyzer (Prevent).
> d_find_alias can return NULL to deentry, Thus we need NULL check
> before calling d_delete(dentry)
>
> Signed-off-by: Maninder Singh <maninder1.s@...sung.com>
> Reviewed-by: Vaneet Narang <v.narang@...sung.com>
> ---
>  fs/devpts/inode.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
> index add5663..0350ac2 100644
> --- a/fs/devpts/inode.c
> +++ b/fs/devpts/inode.c
> @@ -663,7 +663,8 @@ void devpts_pty_kill(struct inode *inode)
>         dentry = d_find_alias(inode);
>
>         drop_nlink(inode);
> -       d_delete(dentry);
> +       if (dentry)
> +               d_delete(dentry);
>         dput(dentry);   /* d_alloc_name() in devpts_pty_new() */
>         dput(dentry);           /* d_find_alias above */

While it is correct that d_find_alias() may return NULL, can this also
happen here?
I mean if that happens in the kill path we might have bigger trouble...

Al?

-- 
Thanks,
//richard
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