From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
Jason Gunthorpe <jgg@ziepe.ca>,
Sean Christopherson <seanjc@google.com>,
Jarkko Sakkinen <jarkko@kernel.org>, Borislav Petkov <bp@suse.de>,
linux-sgx@vger.kernel.org,
Daniel Vetter <daniel.vetter@intel.com>
Subject: [PATCH] x86/sgx: Drop racy follow_pfn check
Date: Thu, 4 Feb 2021 19:45:19 +0100 [thread overview]
Message-ID: <20210204184519.2809313-1-daniel.vetter@ffwll.ch> (raw)
PTE insertion is fundamentally racy, and this check doesn't do
anything useful. Quoting Sean:
"Yeah, it can be whacked. The original, never-upstreamed code asserted that the
resolved PFN matched the PFN being installed by the fault handler as a sanity
check on the SGX driver's EPC management. The WARN assertion got dropped for
whatever reason, leaving that useless chunk."
Jason stumbled over this as a new user of follow_pfn, and I'm trying
to get rid of unsafe callers of that function so it can be locked down
further.
This is independent prep work for the referenced patch series.
References: https://lore.kernel.org/dri-devel/20201127164131.2244124-1-daniel.vetter@ffwll.ch/
Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Sean Christopherson <seanjc@google.com>
Fixes: 947c6e11fa43 ("x86/sgx: Add ptrace() support for the SGX driver")
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: linux-sgx@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
arch/x86/kernel/cpu/sgx/encl.c | 8 --------
1 file changed, 8 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index ee50a5010277..20a2dd5ba2b4 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -141,7 +141,6 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf)
struct sgx_encl_page *entry;
unsigned long phys_addr;
struct sgx_encl *encl;
- unsigned long pfn;
vm_fault_t ret;
encl = vma->vm_private_data;
@@ -168,13 +167,6 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf)
phys_addr = sgx_get_epc_phys_addr(entry->epc_page);
- /* Check if another thread got here first to insert the PTE. */
- if (!follow_pfn(vma, addr, &pfn)) {
- mutex_unlock(&encl->lock);
-
- return VM_FAULT_NOPAGE;
- }
-
ret = vmf_insert_pfn(vma, addr, PFN_DOWN(phys_addr));
if (ret != VM_FAULT_NOPAGE) {
mutex_unlock(&encl->lock);
--
2.30.0
next reply other threads:[~2021-02-04 18:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 18:45 Daniel Vetter [this message]
2021-02-05 2:26 ` [PATCH] x86/sgx: Drop racy follow_pfn check Jarkko Sakkinen
2021-02-05 2:26 ` Jarkko Sakkinen
2021-02-05 7:43 ` Daniel Vetter
2021-02-07 21:16 ` Jarkko Sakkinen
2021-02-05 9:55 ` [tip: x86/sgx] x86/sgx: Drop racy follow_pfn() check tip-bot2 for Daniel Vetter
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210204184519.2809313-1-daniel.vetter@ffwll.ch \
--to=daniel.vetter@ffwll.ch \
--cc=bp@suse.de \
--cc=daniel.vetter@intel.com \
--cc=jarkko@kernel.org \
--cc=jgg@ziepe.ca \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-sgx@vger.kernel.org \
--cc=seanjc@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).