[tip: x86/urgent] x86/sgx: Return VM_FAULT_SIGBUS instead of VM_FAULT_OOM for EPC exhaustion

["tip-bot2 for Haitao Huang" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     6b7b71a70af6d75e0a9eddf4b01e4383a78b8a5e
Gitweb:        https://git.kernel.org/tip/6b7b71a70af6d75e0a9eddf4b01e4383a78b8a5e
Author:        Haitao Huang <haitao.huang@linux.intel.com>
AuthorDate:    Thu, 19 Oct 2023 19:53:53 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 20 Oct 2023 10:05:48 +02:00

x86/sgx: Return VM_FAULT_SIGBUS instead of VM_FAULT_OOM for EPC exhaustion

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")
Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org # v6.0+
---
 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 279148e..d13b7e4 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);