Re: BUG: unable to handle kernel paging request in crypto_sha3_update

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 2 Apr 2024 18:09:21 +0300 Mike Rapoport <rppt@linux.ibm.com> wrote:

> On Tue, Apr 02, 2024 at 04:36:11PM +0800, Herbert Xu wrote:
> > On Wed, Mar 20, 2024 at 10:57:53AM +0800, xingwei lee wrote:
> > >
> > >   syscall(__NR_bind, /*fd=*/r[0], /*addr=*/0x20000000ul, /*addrlen=*/0x58ul);
> > >   res = syscall(__NR_accept, /*fd=*/r[0], /*peer=*/0ul, /*peerlen=*/0ul);
> > >   if (res != -1)
> > >     r[1] = res;
> > >   res = syscall(__NR_memfd_secret, /*flags=*/0ul);
> > >   if (res != -1)
> > >     r[2] = res;
> > 
> > So this is the key to the issue.  The whole point of memfd_secret is
> > to make the pages inaccessible to the kernel.  The issue is those
> > pages are then gifted to the kernel through sendmsg.  Somewhere
> > along the line someone is supposed to throw up an error about this,
> > or map the pages properly.  I guess neither happened which is why
> > we end up with a page fault.
> 
> Yeah, there was a bug in folio_is_secretmem() that should have throw an
> error about this.
> 
> David Hildenbrand sent a fix, it's in Andrew's tree
> 
> https://lore.kernel.org/all/20240326143210.291116-1-david@redhat.com

I'll send "mm/secretmem: fix GUP-fast succeeding on secretmem folios"
upstream this week.