From: Dan Williams <dan.j.williams@intel.com>
To: Dan Williams <dan.j.williams@intel.com>,
Peter Gonda <pgonda@google.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
<linux-coco@lists.linux.dev>, Erdem Aktas <erdemaktas@google.com>,
<peterz@infradead.org>, <linux-kernel@vger.kernel.org>,
<x86@kernel.org>, <dave.hansen@linux.intel.com>
Subject: Re: [PATCH v4 6/6] virt: tdx-guest: Add Quote generation support using TSM_REPORTS
Date: Tue, 10 Oct 2023 12:36:39 -0700 [thread overview]
Message-ID: <6525a7c75a3da_725832947a@dwillia2-xfh.jf.intel.com.notmuch> (raw)
In-Reply-To: <651cb7aa2ea48_ae7e7294a7@dwillia2-xfh.jf.intel.com.notmuch>
Dan Williams wrote:
> Peter Gonda wrote:
> > On Tue, Oct 3, 2023 at 1:29 PM Kuppuswamy Sathyanarayanan
> > <sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
[..]
> > > Dan, do you think it is related to not allocating direct mapped memory (using
> > > kvalloc)?
> >
> > But I think the issue is the stack allocated variable 'ext_req' here:
> >
> > sev_report_new()
> > + void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
> > + if (!buf)
> > + return -ENOMEM;
> > +
> > + guard(mutex)(&snp_cmd_mutex);
> > + certs_address = buf + report_size;
> > + struct snp_ext_report_req ext_req = {
> > + .data = { .vmpl = desc->privlevel },
> > + .certs_address = (__u64)certs_address,
> > + .certs_len = ext_size,
> > + };
> > + memcpy(&ext_req.data.user_data, desc->inblob, desc->inblob_len);
>
> If the failure is coming from:
>
> sg_set_buf(&src[1], src_buf, hdr->msg_sz);
>
> ...then that is always coming from the stack as get_ext_report()
> internally copies either from the user ioctl() address or the kernel
> stack into the local stack copy in both cases:
>
> get_ext_report(...)
> ...
> struct snp_ext_report_req req;
> ...
> if (copy_from_sockptr(&req, io->req_data, sizeof(req)))
> return -EFAULT;
> ...
> ret = handle_guest_request(..., &req.data, ...);
>
> ...where that "&req.data" always becomes the @src_buf argument to
> enc_dec_message(). So while I do understand why sg_set_buf() is
> complaining, I don't understand why it is not *always* complaining,
> regardless of configfs-tsm or ioctl() with CONFIG_DEBUG_SG=y builds.
>
> I will be able to dig deeper once I can test on hardware, but I am
> thinking that the entire scheme to pass the source buffer on the kernel
> stack is broken and is only happening to work because there are no
> crypto-accelerators attached that require that the virtual addresses be
> virt_addr_valid() for a later dma_map_sg() event.
>
> ...or my eyes are overlooking how the ioctl() path is succeeding.
Confirmed, I can make DEBUG_SG equally unhappy via the ioctl() path.
Note I changed the BUG_ON() to WARN_ON() in this kernel to keep the
system alive over reproductions:
WARNING: CPU: 0 PID: 1175 at include/linux/scatterlist.h:187 enc_dec_message+0x518/0x5b0 [sev_guest]
[..]
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
RIP: 0010:enc_dec_message+0x518/0x5b0 [sev_guest]
Call Trace:
<TASK>
[..]
handle_guest_request+0x135/0x520 [sev_guest]
get_ext_report+0x1ec/0x3e0 [sev_guest]
snp_guest_ioctl+0x157/0x200 [sev_guest]
So the required fix here will address both cases.
I will note that on this instance no certificate data is being returned,
so I can't test that path, but at least the report retrieval will be
tested for the next posting of this series.
prev parent reply other threads:[~2023-10-10 19:36 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-26 4:16 [PATCH v4 0/6] configfs-tsm: Attestation Report ABI Dan Williams
2023-09-26 4:17 ` [PATCH v4 1/6] virt: coco: Add a coco/Makefile and coco/Kconfig Dan Williams
2023-09-26 4:17 ` [PATCH v4 2/6] configfs-tsm: Introduce a shared ABI for attestation reports Dan Williams
2023-09-26 18:49 ` Kuppuswamy Sathyanarayanan
2023-09-26 18:59 ` Dan Williams
2023-09-27 0:43 ` Kuppuswamy Sathyanarayanan
2023-09-27 3:17 ` Dan Williams
2023-09-27 8:04 ` Thomas Fossati
2023-09-27 8:21 ` Dan Williams
2023-09-27 8:25 ` Thomas Fossati
2023-09-27 14:38 ` Peter Gonda
2023-09-27 19:05 ` Thomas Fossati
2023-09-27 8:43 ` Thomas Fossati
2023-09-27 2:10 ` Kuppuswamy Sathyanarayanan
2023-09-26 4:17 ` [PATCH v4 3/6] virt: sevguest: Prep for kernel internal {get, get_ext}_report() Dan Williams
2023-09-26 18:51 ` Kuppuswamy Sathyanarayanan
2023-09-26 4:17 ` [PATCH v4 4/6] mm/slab: Add __free() support for kvfree Dan Williams
2023-09-26 4:17 ` [PATCH v4 5/6] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}_REPORT Dan Williams
2023-10-04 8:22 ` Dan Carpenter
2023-09-26 4:17 ` [PATCH v4 6/6] virt: tdx-guest: Add Quote generation support using TSM_REPORTS Dan Williams
2023-09-27 16:14 ` Peter Gonda
2023-09-27 16:53 ` Dan Williams
2023-09-28 22:49 ` Dan Williams
2023-09-29 17:26 ` Peter Gonda
2023-10-03 18:37 ` Peter Gonda
2023-10-03 19:29 ` Kuppuswamy Sathyanarayanan
2023-10-03 20:06 ` Peter Gonda
2023-10-04 0:54 ` Dan Williams
2023-10-10 19:36 ` Dan Williams [this message]
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