Re: [PATCH] macintosh:fix oob read in do_adb_query function

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2022-07-13 at 11:53 -0700, Kees Cook wrote:
> On Wed, Jul 13, 2022 at 11:37:34PM +0800, Ning Qiang wrote:
> > In do_adb_query function of drivers/macintosh/adb.c, req->data is
> > copy
> > form userland. the  parameter "req->data[2]" is Missing check, the
> > array size of adb_handler[] is 16, so "adb_handler[
> > req->data[2]].original_address" and "adb_handler[
> > req->data[2]].handler_id" will lead to oob read.
> > 
> > Signed-off-by: Ning Qiang <sohu0106@126.com>
> 
> Thanks for catching this!
> 
> Do you have a reproducer for this? I'd expect CONFIG_UBSAN_BOUNDS=y
> to notice this at runtime, at least.

For that you would need an ancient Mac with an ADB bus which might be
tricky ... I have some in the basement that could possibly be revived
if you really insist but I'd rather not waste the time...

Cheers,
Ben.

> 
> > ---
> >  drivers/macintosh/adb.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/macintosh/adb.c b/drivers/macintosh/adb.c
> > index 439fab4eaa85..1bbb9ca08d40 100644
> > --- a/drivers/macintosh/adb.c
> > +++ b/drivers/macintosh/adb.c
> > @@ -647,7 +647,7 @@ do_adb_query(struct adb_request *req)
> >  
> >  	switch(req->data[1]) {
> >  	case ADB_QUERY_GETDEVINFO:
> > -		if (req->nbytes < 3)
> > +		if (req->nbytes < 3 || req->data[2] >= 16)
> 
> I'd prefer this was:
> 
> +		if (req->nbytes < 3 || req->data[2] >=
> ARRAY_SIZE(adb_handler))
> 
> so it's tied to the actual variable (if its size ever changes).
> 
> With that:
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 
> -Kees
> 
> >  			break;
> >  		mutex_lock(&adb_handler_mutex);
> >  		req->reply[0] = adb_handler[req-
> > >data[2]].original_address;
> > -- 
> > 2.25.1
> >