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

[Greg Kroah-Hartman]

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?

thanks,

greg k-h