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

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On Fri Oct 20, 2023 at 5:53 AM EEST, Haitao Huang wrote:
> 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@xxxxxxxxxxxxxxx # v6.0+
> Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
> ---
>  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);
>  

Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>

BR, Jarkko




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