netdev - Re: [PATCH 5.19 005/192] net: mvpp2: debugfs: fix memory leak when using debugfs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YyC0eveBK8UzeIdI@shell.armlinux.org.uk>
Date:   Tue, 13 Sep 2022 17:48:58 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Marcin Wojtas <mw@...ihalf.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        stable <stable@...nel.org>
Subject: Re: [PATCH 5.19 005/192] net: mvpp2: debugfs: fix memory leak when
 using debugfs_lookup()

On Tue, Sep 13, 2022 at 04:01:51PM +0200, Greg Kroah-Hartman wrote:
> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> commit fe2c9c61f668cde28dac2b188028c5299cedcc1e upstream.
> 
> When calling debugfs_lookup() the result must have dput() called on it,
> otherwise the memory will leak over time.  Fix this up to be much
> simpler logic and only create the root debugfs directory once when the
> driver is first accessed.  That resolves the memory leak and makes
> things more obvious as to what the intent is.
> 
> Cc: Marcin Wojtas <mw@...ihalf.com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: netdev@...r.kernel.org
> Cc: stable <stable@...nel.org>
> Fixes: 21da57a23125 ("net: mvpp2: add a debugfs interface for the Header Parser")
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c
> @@ -700,10 +700,10 @@ void mvpp2_dbgfs_cleanup(struct mvpp2 *p
>  
>  void mvpp2_dbgfs_init(struct mvpp2 *priv, const char *name)
>  {
> -	struct dentry *mvpp2_dir, *mvpp2_root;
> +	static struct dentry *mvpp2_root;
> +	struct dentry *mvpp2_dir;
>  	int ret, i;
>  
> -	mvpp2_root = debugfs_lookup(MVPP2_DRIVER_NAME, NULL);
>  	if (!mvpp2_root)
>  		mvpp2_root = debugfs_create_dir(MVPP2_DRIVER_NAME, NULL);

This looks broken to me.

What happens if this is built as a module, and the module is loaded,
binds (and creates the directory), then is removed, and then re-
inserted?  Nothing removes the old directory, so doesn't
debugfs_create_dir() fail, resulting in subsequent failure to add
any subsequent debugfs entries?

I don't think this patch should be backported to stable trees until
this point is addressed.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!