[PATCH] x86/sgx: Return VM_FAULT_SIGBUS for EPC exhaustion

From: Haitao Huang <haitao.huang@linux.intel.com>
To: jarkko@kernel.org, dave.hansen@linux.intel.com,
	linux-sgx@vger.kernel.org, x86@kernel.org
Cc: reinette.chatre@intel.com, kai.huang@intel.com,
	Haitao Huang <haitao.huang@linux.intel.com>,
	stable@vger.kernel.org
Subject: [PATCH] x86/sgx: Return VM_FAULT_SIGBUS for EPC exhaustion
Date: Thu, 19 Oct 2023 19:53:53 -0700	[thread overview]
Message-ID: <20231020025353.29691-1-haitao.huang@linux.intel.com> (raw)

In the EAUG on page fault path, VM_FAULT_OOM is returned when the
Enclave Page Cache (EPC) runs out. This may trigger unneeded OOM kill
that will not free any EPCs. Return VM_FAULT_SIGBUS instead.

Fixes: 5a90d2c3f5ef ("x86/sgx: Support adding of pages to an initialized enclave")
Cc: stable@vger.kernel.org # v6.0+
Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
---
 arch/x86/kernel/cpu/sgx/encl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 279148e72459..d13b7e4ad0f5 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -322,7 +322,7 @@ struct sgx_encl_page *sgx_encl_load_page(struct sgx_encl *encl,
  * ENCLS[EAUG] instruction.
  *
  * Returns: Appropriate vm_fault_t: VM_FAULT_NOPAGE when PTE was installed
- * successfully, VM_FAULT_SIGBUS or VM_FAULT_OOM as error otherwise.
+ * successfully, VM_FAULT_SIGBUS as error otherwise.
  */
 static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
 				     struct sgx_encl *encl, unsigned long addr)
@@ -348,7 +348,7 @@ static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
 	secinfo_flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_X;
 	encl_page = sgx_encl_page_alloc(encl, addr - encl->base, secinfo_flags);
 	if (IS_ERR(encl_page))
-		return VM_FAULT_OOM;
+		return VM_FAULT_SIGBUS;
 
 	mutex_lock(&encl->lock);
 
-- 
2.25.1

