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

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 <[email protected]>
AuthorDate: Thu, 19 Oct 2023 19:53:53 -07:00
Committer: Ingo Molnar <[email protected]>
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 <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: [email protected] # 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);


2023-10-26 22:56:57

by Haitao Huang

[permalink] [raw]
Subject: [PATCH] Revert "x86/sgx: Return VM_FAULT_SIGBUS instead of VM_FAULT_OOM for EPC exhaustion"

This reverts commit 6b7b71a70af6d75e0a9eddf4b01e4383a78b8a5e.
That patch was a mistake.

link: https://lore.kernel.org/all/[email protected]/

Signed-off-by: Haitao Huang <[email protected]>
---
Sorry for the trouble. Please use this to revert or drop it from the
the tip/x86/urgent branch.
---
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 d13b7e4ad0f5..279148e72459 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 as error otherwise.
+ * successfully, VM_FAULT_SIGBUS or VM_FAULT_OOM 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_SIGBUS;
+ return VM_FAULT_OOM;

mutex_lock(&encl->lock);

--
2.25.1

2023-10-27 17:22:34

by Dave Hansen

[permalink] [raw]
Subject: Re: [PATCH] Revert "x86/sgx: Return VM_FAULT_SIGBUS instead of VM_FAULT_OOM for EPC exhaustion"

On 10/26/23 15:55, Haitao Huang wrote:
> This reverts commit 6b7b71a70af6d75e0a9eddf4b01e4383a78b8a5e. That patch
> was a mistake. link:
> https://lore.kernel.org/all/[email protected]/

Thanks for the patch. There was only one trivial commit on top, so I
just dropped your commit and effectively rebased the other single one
instead of applying a revert.