On Sat, 29 Jun 2019 at 11:11, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Sat, Jun 29, 2019 at 10:47:00AM +0200, Ard Biesheuvel wrote: > > On Sat, 29 Jun 2019 at 08:57, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Fri, Jun 28, 2019 at 11:42:13AM -0700, Srivatsa S. Bhat wrote: > > > > From: Gen Zhang <blackgod016574@xxxxxxxxx> > > > > > > > > commit 4e78921ba4dd0aca1cc89168f45039add4183f8e upstream. > > > > > > > > The old_memmap flow in efi_call_phys_prolog() performs numerous memory > > > > allocations, and either does not check for failure at all, or it does > > > > but fails to propagate it back to the caller, which may end up calling > > > > into the firmware with an incomplete 1:1 mapping. > > > > > > > > So let's fix this by returning NULL from efi_call_phys_prolog() on > > > > memory allocation failures only, and by handling this condition in the > > > > caller. Also, clean up any half baked sets of page tables that we may > > > > have created before returning with a NULL return value. > > > > > > > > Note that any failure at this level will trigger a panic() two levels > > > > up, so none of this makes a huge difference, but it is a nice cleanup > > > > nonetheless. > > > > > > With a description like this, why is this needed in a stable kernel if > > > it does not really fix anything useful? > > > > > > > Because it fixes a 'CVE', remember? :-) > > No, I don't remember that at all. > > Remember, I get 1000+ emails a day to do something with, and hence, have > the short-term memory of prior emails of a squirrel. > > Also, CVEs mean nothing, anyone can get one and they are impossible to > revoke, so don't treat them like they are "authoritative" at all. > To refresh your memory: I already nacked this backport once before, on the grounds that the CVE is completely bogus.
