x86/mm/pkeys: Pass VMA down in to fault signal generation code

During a page fault, we look up the VMA to ensure that the fault
is in a region with a valid mapping.  But, in the top-level page
fault code we don't need the VMA for much else.  Once we have
decided that an access is bad, we are going to send a signal no
matter what and do not need the VMA any more.  So we do not pass
it down in to the signal generation code.

But, for protection keys, we need the VMA.  It tells us *which*
protection key we violated if we get a PF_PK.  So, we need to
pass the VMA down and fill in siginfo->si_pkey.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210211.AD3B36A3@viggo.jf.intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/fault.c

@@ -171,7 +171,8 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
 
 static void
 force_sig_info_fault(int si_signo, int si_code, unsigned long address,
-		     struct task_struct *tsk, int fault)
+		     struct task_struct *tsk, struct vm_area_struct *vma,
+		     int fault)
 {
 	unsigned lsb = 0;
 	siginfo_t info;
@@ -656,6 +657,8 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 	struct task_struct *tsk = current;
 	unsigned long flags;
 	int sig;
+	/* No context means no VMA to pass down */
+	struct vm_area_struct *vma = NULL;
 
 	/* Are we prepared to handle this kernel fault? */
 	if (fixup_exception(regs)) {
@@ -679,7 +682,8 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 			tsk->thread.cr2 = address;
 
 			/* XXX: hwpoison faults will set the wrong code. */
-			force_sig_info_fault(signal, si_code, address, tsk, 0);
+			force_sig_info_fault(signal, si_code, address,
+					     tsk, vma, 0);
 		}
 
 		/*
@@ -756,7 +760,8 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code,
 
 static void
 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
-		       unsigned long address, int si_code)
+		       unsigned long address, struct vm_area_struct *vma,
+		       int si_code)
 {
 	struct task_struct *tsk = current;
 
@@ -799,7 +804,7 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 		tsk->thread.error_code	= error_code;
 		tsk->thread.trap_nr	= X86_TRAP_PF;
 
-		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
+		force_sig_info_fault(SIGSEGV, si_code, address, tsk, vma, 0);
 
 		return;
 	}
@@ -812,14 +817,14 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 static noinline void
 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
-		     unsigned long address)
+		     unsigned long address, struct vm_area_struct *vma)
 {
-	__bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
+	__bad_area_nosemaphore(regs, error_code, address, vma, SEGV_MAPERR);
 }
 
 static void
 __bad_area(struct pt_regs *regs, unsigned long error_code,
-	   unsigned long address, int si_code)
+	   unsigned long address,  struct vm_area_struct *vma, int si_code)
 {
 	struct mm_struct *mm = current->mm;
 
@@ -829,25 +834,25 @@ __bad_area(struct pt_regs *regs, unsigned long error_code,
 	 */
 	up_read(&mm->mmap_sem);
 
-	__bad_area_nosemaphore(regs, error_code, address, si_code);
+	__bad_area_nosemaphore(regs, error_code, address, vma, si_code);
 }
 
 static noinline void
 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 {
-	__bad_area(regs, error_code, address, SEGV_MAPERR);
+	__bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
 }
 
 static noinline void
 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
-		      unsigned long address)
+		      unsigned long address, struct vm_area_struct *vma)
 {
-	__bad_area(regs, error_code, address, SEGV_ACCERR);
+	__bad_area(regs, error_code, address, vma, SEGV_ACCERR);
 }
 
 static void
 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
-	  unsigned int fault)
+	  struct vm_area_struct *vma, unsigned int fault)
 {
 	struct task_struct *tsk = current;
 	int code = BUS_ADRERR;
@@ -874,12 +879,13 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 		code = BUS_MCEERR_AR;
 	}
 #endif
-	force_sig_info_fault(SIGBUS, code, address, tsk, fault);
+	force_sig_info_fault(SIGBUS, code, address, tsk, vma, fault);
 }
 
 static noinline void
 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
-	       unsigned long address, unsigned int fault)
+	       unsigned long address, struct vm_area_struct *vma,
+	       unsigned int fault)
 {
 	if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
 		no_context(regs, error_code, address, 0, 0);
@@ -903,9 +909,9 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 	} else {
 		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
 			     VM_FAULT_HWPOISON_LARGE))
-			do_sigbus(regs, error_code, address, fault);
+			do_sigbus(regs, error_code, address, vma, fault);
 		else if (fault & VM_FAULT_SIGSEGV)
-			bad_area_nosemaphore(regs, error_code, address);
+			bad_area_nosemaphore(regs, error_code, address, vma);
 		else
 			BUG();
 	}
@@ -1119,7 +1125,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 		 * Don't take the mm semaphore here. If we fixup a prefetch
 		 * fault we could otherwise deadlock:
 		 */
-		bad_area_nosemaphore(regs, error_code, address);
+		bad_area_nosemaphore(regs, error_code, address, NULL);
 
 		return;
 	}
@@ -1132,7 +1138,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 		pgtable_bad(regs, error_code, address);
 
 	if (unlikely(smap_violation(error_code, regs))) {
-		bad_area_nosemaphore(regs, error_code, address);
+		bad_area_nosemaphore(regs, error_code, address, NULL);
 		return;
 	}
 
@@ -1141,7 +1147,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 	 * in a region with pagefaults disabled then we must not take the fault
 	 */
 	if (unlikely(faulthandler_disabled() || !mm)) {
-		bad_area_nosemaphore(regs, error_code, address);
+		bad_area_nosemaphore(regs, error_code, address, NULL);
 		return;
 	}
 
@@ -1185,7 +1191,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
 		if ((error_code & PF_USER) == 0 &&
 		    !search_exception_tables(regs->ip)) {
-			bad_area_nosemaphore(regs, error_code, address);
+			bad_area_nosemaphore(regs, error_code, address, NULL);
 			return;
 		}
 retry:
@@ -1233,7 +1239,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 	 */
 good_area:
 	if (unlikely(access_error(error_code, vma))) {
-		bad_area_access_error(regs, error_code, address);
+		bad_area_access_error(regs, error_code, address, vma);
 		return;
 	}
 
@@ -1271,7 +1277,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 
 	up_read(&mm->mmap_sem);
 	if (unlikely(fault & VM_FAULT_ERROR)) {
-		mm_fault_error(regs, error_code, address, fault);
+		mm_fault_error(regs, error_code, address, vma, fault);
 		return;
 	}