From: Daniel Vetter daniel.vetter@ffwll.ch
mainline inclusion from mainline-v5.12-rc1-dontuse commit dc9b7be557ca94301ea5c06c0d72307e642ffb18 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I4SIGI CVE: NA
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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:
https://lore.kernel.org/dri-devel/20201127164131.2244124-1-daniel.vetter@ffw...
Intel-SIG: commit dc9b7be557ca x86/sgx: Drop racy follow_pfn() check Backport for SGX Foundations support
Fixes: 947c6e11fa43 ("x86/sgx: Add ptrace() support for the SGX driver") Reported-by: Jason Gunthorpe jgg@ziepe.ca Signed-off-by: Daniel Vetter daniel.vetter@intel.com Signed-off-by: Borislav Petkov bp@suse.de Reviewed-by: Jarkko Sakkinen jarkko@kernel.org Link: https://lkml.kernel.org/r/20210204184519.2809313-1-daniel.vetter@ffwll.ch Signed-off-by: Fan Du fan.du@intel.com #openEuler_contributor Signed-off-by: Laibin Qiu qiulaibin@huawei.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);