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From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc:     "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
        linux-sgx@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>,
        Josh Triplett <josh@joshtriplett.org>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Jethro Beekman <jethro@fortanix.com>,
        "Dr . Greg Wettstein" <greg@enjellic.com>
Subject: [RFC PATCH v4 3/5] x86/fault: Attempt to fixup unhandled #PF on ENCLU before signaling
Date:   Thu, 13 Dec 2018 13:31:33 -0800
Message-Id: <20181213213135.12913-4-sean.j.christopherson@intel.com>
In-Reply-To: <20181213213135.12913-1-sean.j.christopherson@intel.com>
References: <20181213213135.12913-1-sean.j.christopherson@intel.com>
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Call fixup_sgx_enclu_exception() in the SIGSEGV and SIGBUS paths of
the page fault handler immediately prior to signaling.  If the fault
is fixed, return cleanly and do not generate a signal.

In the SIGSEGV flow, make sure the error code passed to userspace has
been sanitized.

Suggested-by: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/mm/fault.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index fefeb745d21d..c6f5f77ffabd 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -28,6 +28,7 @@
 #include <asm/mmu_context.h>		/* vma_pkey()			*/
 #include <asm/efi.h>			/* efi_recover_from_page_fault()*/
 #include <asm/desc.h>			/* store_idt(), ...		*/
+#include <asm/vdso.h>			/* fixup_vdso_exception()	*/
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -928,6 +929,9 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 		sanitize_error_code(address, &error_code);
 
+		if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
+			return;
+
 		if (likely(show_unhandled_signals))
 			show_signal_msg(regs, error_code, address, tsk);
 
@@ -1047,6 +1051,9 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 
 	sanitize_error_code(address, &error_code);
 
+	if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
+		return;
+
 	set_signal_archinfo(address, error_code);
 
 #ifdef CONFIG_MEMORY_FAILURE
-- 
2.19.2