linux-kernel - Re: [PATCH] Revert "consolemap: Fix a memory leaking bug in drivers/tty/vt/consolemap.c"

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Message-ID: <20190604190234.GA10572@kroah.com>
Date:   Tue, 4 Jun 2019 21:02:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ben Hutchings <ben@...adent.org.uk>
Cc:     Jiri Slaby <jslaby@...e.com>, Gen Zhang <blackgod016574@...il.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "consolemap: Fix a memory leaking bug in
 drivers/tty/vt/consolemap.c"

On Tue, Jun 04, 2019 at 07:00:39PM +0100, Ben Hutchings wrote:
> This reverts commit 84ecc2f6eb1cb12e6d44818f94fa49b50f06e6ac.
> 
> con_insert_unipair() is working with a sparse 3-dimensional array:
> 
> - p->uni_pgdir[] is the top layer
> - p1 points to a middle layer
> - p2 points to a bottom layer
> 
> If it needs to allocate a new middle layer, and then fails to allocate
> a new bottom layer, it would previously free only p2, and now it frees
> both p1 and p2.  But since the new middle layer was already registered
> in the top layer, it was not leaked.
> 
> However, if it looks up an *existing* middle layer and then fails to
> allocate a bottom layer, it now frees both p1 and p2 but does *not*
> free any other bottom layers under p1.  So it *introduces* a memory
> leak.
> 
> The error path also cleared the wrong index in p->uni_pgdir[],
> introducing a use-after-free.
> 
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>

Now applied, thanks.

Gen, please be careful with these types of "fixes"...

thanks,

greg k-h