From: Mike Rapoport <rppt@linux.ibm.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: xingwei lee <xrivendell7@gmail.com>,
davem@davemloft.net, linux-crypto@vger.kernel.org,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
samsun1006219@gmail.com,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org
Subject: Re: BUG: unable to handle kernel paging request in crypto_sha3_update
Date: Tue, 2 Apr 2024 18:09:21 +0300 [thread overview]
Message-ID: <ZgwfoSj7GqFiOOsc@linux.ibm.com> (raw)
In-Reply-To: <ZgvDe6fdJzgb8aZZ@gondor.apana.org.au>
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 cc the memfd_secret authors to see what should catch this.
>
> > syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0xb36000ul,
> > /*prot=*/0x2000003ul, /*flags=*/0x28011ul, /*fd=*/r[2],
> > /*offset=*/0ul);
> > syscall(__NR_ftruncate, /*fd=*/r[2], /*len=*/0xde99ul);
> > *(uint64_t*)0x20000180 = 0;
> > *(uint32_t*)0x20000188 = 0;
> > *(uint64_t*)0x20000190 = 0x20000140;
> > *(uint64_t*)0x20000140 = 0x20000080;
> > *(uint64_t*)0x20000148 = 0xb0;
> > *(uint64_t*)0x20000198 = 1;
> > *(uint64_t*)0x200001a0 = 0;
> > *(uint64_t*)0x200001a8 = 0;
> > *(uint32_t*)0x200001b0 = 0;
> > syscall(__NR_sendmsg, /*fd=*/r[1], /*msg=*/0x20000180ul,
> > /*f=*/0x47933e2b0522cf63ul);
>
> This is the spot where the memfd_secret pages are given to the kernel
> for processing through sendmsg.
>
> Thanks,
> --
> Email: Herbert Xu <herbert@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2024-04-02 15:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-20 2:57 BUG: unable to handle kernel paging request in crypto_sha3_update xingwei lee
2024-04-02 8:36 ` Herbert Xu
2024-04-02 15:09 ` Mike Rapoport [this message]
2024-04-02 17:10 ` Andrew Morton
2024-04-03 4:34 ` Herbert Xu
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