| Message ID | 20190903142655.21943-4-jarkko.sakkinen@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Intel SGX foundations | expand |
On Tue, Sep 03, 2019 at 05:26:34PM +0300, Jarkko Sakkinen wrote: > From: Sean Christopherson <sean.j.christopherson@intel.com> > > Include SGX bit to the PF error codes and throw SIGSEGV with PF_SGX when > a #PF with SGX set happens. > > CPU throws a #PF with the SGX bit in the event of Enclave Page Cache Map > (EPCM) conflict. The EPCM is a CPU-internal table, which describes the > properties for a enclave page. Enclaves are measured and signed software > entities, which SGX hosts. [1] > > Although the primary purpose of the EPCM conflict checks is to prevent > malicious accesses to an enclave, an illegit access can happen also for > legit reasons. > > All SGX reserved memory, including EPCM is encrypted with a transient > key that does not survive from the power transition. Throwing a SIGSEGV > allows user space software react when this happens (e.g. rec-create the > enclave, which was invalidated). > > [1] Intel SDM: 36.5.1 Enclave Page Cache Map (EPCM) > > Cc: Andy Lutomirski <luto@amacapital.net> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> > --- > arch/x86/include/asm/traps.h | 1 + > arch/x86/mm/fault.c | 13 +++++++++++++ > 2 files changed, 14 insertions(+) > > diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h > index b25e633033c3..81472cae4024 100644 > --- a/arch/x86/include/asm/traps.h > +++ b/arch/x86/include/asm/traps.h > @@ -171,5 +171,6 @@ enum x86_pf_error_code { > X86_PF_RSVD = 1 << 3, > X86_PF_INSTR = 1 << 4, > X86_PF_PK = 1 << 5, > + X86_PF_SGX = 1 << 15, > }; > #endif /* _ASM_X86_TRAPS_H */ > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index 9ceacd1156db..c2dea3f9e263 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -1178,6 +1178,19 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) > if (error_code & X86_PF_PK) > return 1; > > + /* > + * Access is blocked by the Enclave Page Cache Map (EPCM), i.e. the > + * access is allowed by the PTE but not the EPCM. This usually happens > + * when the EPCM is yanked out from under us, e.g. by hardware after a > + * suspend/resume cycle. In any case, software, i.e. the kernel, can't > + * fix the source of the fault as the EPCM can't be directly modified > + * by software. Handle the fault as an access error in order to signal > + * userspace, e.g. so that userspace can rebuild their enclave(s), even s/, e.g.//
On Tue, Sep 24, 2019 at 06:04:42PM +0200, Borislav Petkov wrote: > > + /* > > + * Access is blocked by the Enclave Page Cache Map (EPCM), i.e. the > > + * access is allowed by the PTE but not the EPCM. This usually happens > > + * when the EPCM is yanked out from under us, e.g. by hardware after a > > + * suspend/resume cycle. In any case, software, i.e. the kernel, can't > > + * fix the source of the fault as the EPCM can't be directly modified > > + * by software. Handle the fault as an access error in order to signal > > + * userspace, e.g. so that userspace can rebuild their enclave(s), even > > s/, e.g.// Thanks I fixed this in my tree. Also, quite many sentences seem that have two spacebars after the end of sentence. I fixed those too. /Jarkko
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index b25e633033c3..81472cae4024 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -171,5 +171,6 @@ enum x86_pf_error_code { X86_PF_RSVD = 1 << 3, X86_PF_INSTR = 1 << 4, X86_PF_PK = 1 << 5, + X86_PF_SGX = 1 << 15, }; #endif /* _ASM_X86_TRAPS_H */ diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9ceacd1156db..c2dea3f9e263 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1178,6 +1178,19 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) if (error_code & X86_PF_PK) return 1; + /* + * Access is blocked by the Enclave Page Cache Map (EPCM), i.e. the + * access is allowed by the PTE but not the EPCM. This usually happens + * when the EPCM is yanked out from under us, e.g. by hardware after a + * suspend/resume cycle. In any case, software, i.e. the kernel, can't + * fix the source of the fault as the EPCM can't be directly modified + * by software. Handle the fault as an access error in order to signal + * userspace, e.g. so that userspace can rebuild their enclave(s), even + * though userspace may not have actually violated access permissions. + */ + if (unlikely(error_code & X86_PF_SGX)) + return 1; + /* * Make sure to check the VMA so that we do not perform * faults just to hit a X86_PF_PK as soon as we fill in a