Re: [PATCH 4.17 154/220] UBIFS: Fix potential integer overflow in allocation

[Greg Kroah-Hartman]

On Mon, Jul 02, 2018 at 08:32:55AM +0200, Greg Kroah-Hartman wrote:
> On Sun, Jul 01, 2018 at 08:48:07PM +0200, Richard Weinberger wrote:
> > On Sun, Jul 1, 2018 at 6:22 PM, Greg Kroah-Hartman
> > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > > 4.17-stable review patch.  If anyone has any objections, please let me know.
> > >
> > > ------------------
> > >
> > > From: Silvio Cesare <silvio.cesare@xxxxxxxxx>
> > >
> > > commit 353748a359f1821ee934afc579cf04572406b420 upstream.
> > >
> > > There is potential for the size and len fields in ubifs_data_node to be
> > > too large causing either a negative value for the length fields or an
> > > integer overflow leading to an incorrect memory allocation. Likewise,
> > > when the len field is small, an integer underflow may occur.
> > >
> > > Signed-off-by: Silvio Cesare <silvio.cesare@xxxxxxxxx>
> > > Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > 
> > Guys, this patch was never on linux-mtd nor was I CC'ed.
> > I don't see it so super security critical which argues to bypass the
> > whole community review process.
> > 
> > Anyway, I don't like this patch for two reasons.
> > 1. Instead of doing the kmalloc_array() dance, just check whether size
> > is 0 > and <= UBIFS_BLOCK_SIZE, in the caller.
> > 2. It will not apply to most stable kernels since it targets the code
> > path with UBIFS encryption available.
> 
> Can you get a fix into Linus's tree that I can also queue up for a
> stable release?

Ah nevermind, I see your revert/add patch now, sorry for the noise.

greg k-h