1 files changed, 184 insertions, 84 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index f0b4caf85c1..36642793e31 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -8,16 +8,21 @@
 #include <linux/kdebug.h>		/* oops_begin/end, ...		*/
 #include <linux/module.h>		/* search_exception_table	*/
 #include <linux/bootmem.h>		/* max_low_pfn			*/
-#include <linux/kprobes.h>		/* __kprobes, ...		*/
+#include <linux/kprobes.h>		/* NOKPROBE_SYMBOL, ...		*/
 #include <linux/mmiotrace.h>		/* kmmio_handler, ...		*/
 #include <linux/perf_event.h>		/* perf_sw_event		*/
 #include <linux/hugetlb.h>		/* hstate_index_to_shift	*/
 #include <linux/prefetch.h>		/* prefetchw			*/
+#include <linux/context_tracking.h>	/* exception_enter(), ...	*/
 
 #include <asm/traps.h>			/* dotraplinkage, ...		*/
 #include <asm/pgalloc.h>		/* pgd_*(), ...			*/
 #include <asm/kmemcheck.h>		/* kmemcheck_*(), ...		*/
-#include <asm/fixmap.h>			/* VSYSCALL_START		*/
+#include <asm/fixmap.h>			/* VSYSCALL_ADDR		*/
+#include <asm/vsyscall.h>		/* emulate_vsyscall		*/
+
+#define CREATE_TRACE_POINTS
+#include <asm/trace/exceptions.h>
 
 /*
  * Page fault error code bits:
@@ -41,7 +46,7 @@ enum x86_pf_error_code {
  * Returns 0 if mmiotrace is disabled, or if the fault is not
  * handled by mmiotrace:
  */
-static inline int __kprobes
+static nokprobe_inline int
 kmmio_fault(struct pt_regs *regs, unsigned long addr)
 {
 	if (unlikely(is_kmmio_active()))
@@ -50,7 +55,7 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr)
 	return 0;
 }
 
-static inline int __kprobes notify_page_fault(struct pt_regs *regs)
+static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
 {
 	int ret = 0;
 
@@ -257,7 +262,7 @@ void vmalloc_sync_all(void)
  *
  *   Handle a fault on the vmalloc or module mapping area
  */
-static noinline __kprobes int vmalloc_fault(unsigned long address)
+static noinline int vmalloc_fault(unsigned long address)
 {
 	unsigned long pgd_paddr;
 	pmd_t *pmd_k;
@@ -287,6 +292,7 @@ static noinline __kprobes int vmalloc_fault(unsigned long address)
 
 	return 0;
 }
+NOKPROBE_SYMBOL(vmalloc_fault);
 
 /*
  * Did it hit the DOS screen memory VA from vm86 mode?
@@ -354,7 +360,7 @@ void vmalloc_sync_all(void)
  *
  * This assumes no large pages in there.
  */
-static noinline __kprobes int vmalloc_fault(unsigned long address)
+static noinline int vmalloc_fault(unsigned long address)
 {
 	pgd_t *pgd, *pgd_ref;
 	pud_t *pud, *pud_ref;
@@ -377,10 +383,12 @@ static noinline __kprobes int vmalloc_fault(unsigned long address)
 	if (pgd_none(*pgd_ref))
 		return -1;
 
-	if (pgd_none(*pgd))
+	if (pgd_none(*pgd)) {
 		set_pgd(pgd, *pgd_ref);
-	else
+		arch_flush_lazy_mmu_mode();
+	} else {
 		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
+	}
 
 	/*
 	 * Below here mismatches are bugs because these lower tables
@@ -419,6 +427,7 @@ static noinline __kprobes int vmalloc_fault(unsigned long address)
 
 	return 0;
 }
+NOKPROBE_SYMBOL(vmalloc_fault);
 
 #ifdef CONFIG_CPU_SUP_AMD
 static const char errata93_warning[] =
@@ -554,7 +563,7 @@ static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
 	/*
 	 * Pentium F0 0F C7 C8 bug workaround:
 	 */
-	if (boot_cpu_data.f00f_bug) {
+	if (boot_cpu_has_bug(X86_BUG_F00F)) {
 		nr = (address - idt_descr.address) >> 3;
 
 		if (nr == 6) {
@@ -578,11 +587,16 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 
 	if (error_code & PF_INSTR) {
 		unsigned int level;
+		pgd_t *pgd;
+		pte_t *pte;
 
-		pte_t *pte = lookup_address(address, &level);
+		pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
+		pgd += pgd_index(address);
+
+		pte = lookup_address_in_pgd(pgd, address, &level);
 
 		if (pte && pte_present(*pte) && !pte_exec(*pte))
-			printk(nx_warning, current_uid());
+			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
 	}
 
 	printk(KERN_ALERT "BUG: unable to handle kernel ");
@@ -593,7 +607,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 
 	printk(KERN_CONT " at %p\n", (void *) address);
 	printk(KERN_ALERT "IP:");
-	printk_address(regs->ip, 1);
+	printk_address(regs->ip);
 
 	dump_pagetable(address);
 }
@@ -615,7 +629,7 @@ pgtable_bad(struct pt_regs *regs, unsigned long error_code,
 	dump_pagetable(address);
 
 	tsk->thread.cr2		= address;
-	tsk->thread.trap_no	= 14;
+	tsk->thread.trap_nr	= X86_TRAP_PF;
 	tsk->thread.error_code	= error_code;
 
 	if (__die("Bad pagetable", regs, error_code))
@@ -635,14 +649,32 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 
 	/* Are we prepared to handle this kernel fault? */
 	if (fixup_exception(regs)) {
+		/*
+		 * Any interrupt that takes a fault gets the fixup. This makes
+		 * the below recursive fault logic only apply to a faults from
+		 * task context.
+		 */
+		if (in_interrupt())
+			return;
+
+		/*
+		 * Per the above we're !in_interrupt(), aka. task context.
+		 *
+		 * In this case we need to make sure we're not recursively
+		 * faulting through the emulate_vsyscall() logic.
+		 */
 		if (current_thread_info()->sig_on_uaccess_error && signal) {
-			tsk->thread.trap_no = 14;
+			tsk->thread.trap_nr = X86_TRAP_PF;
 			tsk->thread.error_code = error_code | PF_USER;
 			tsk->thread.cr2 = address;
 
 			/* XXX: hwpoison faults will set the wrong code. */
 			force_sig_info_fault(signal, si_code, address, tsk, 0);
 		}
+
+		/*
+		 * Barring that, we can do the fixup and be happy.
+		 */
 		return;
 	}
 
@@ -676,7 +708,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
 
 	tsk->thread.cr2		= address;
-	tsk->thread.trap_no	= 14;
+	tsk->thread.trap_nr	= X86_TRAP_PF;
 	tsk->thread.error_code	= error_code;
 
 	sig = SIGKILL;
@@ -742,19 +774,21 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 		 * emulation.
 		 */
 		if (unlikely((error_code & PF_INSTR) &&
-			     ((address & ~0xfff) == VSYSCALL_START))) {
+			     ((address & ~0xfff) == VSYSCALL_ADDR))) {
 			if (emulate_vsyscall(regs, address))
 				return;
 		}
 #endif
+		/* Kernel addresses are always protection faults: */
+		if (address >= TASK_SIZE)
+			error_code |= PF_PROT;
 
-		if (unlikely(show_unhandled_signals))
+		if (likely(show_unhandled_signals))
 			show_signal_msg(regs, error_code, address, tsk);
 
-		/* Kernel addresses are always protection faults: */
 		tsk->thread.cr2		= address;
-		tsk->thread.error_code	= error_code | (address >= TASK_SIZE);
-		tsk->thread.trap_no	= 14;
+		tsk->thread.error_code	= error_code;
+		tsk->thread.trap_nr	= X86_TRAP_PF;
 
 		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
 
@@ -802,20 +836,6 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
 	__bad_area(regs, error_code, address, SEGV_ACCERR);
 }
 
-/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
-static void
-out_of_memory(struct pt_regs *regs, unsigned long error_code,
-	      unsigned long address)
-{
-	/*
-	 * We ran out of memory, call the OOM killer, and return the userspace
-	 * (which will retry the fault, or kill us if we got oom-killed):
-	 */
-	up_read(&current->mm->mmap_sem);
-
-	pagefault_out_of_memory();
-}
-
 static void
 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 	  unsigned int fault)
@@ -838,7 +858,7 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 
 	tsk->thread.cr2		= address;
 	tsk->thread.error_code	= error_code;
-	tsk->thread.trap_no	= 14;
+	tsk->thread.trap_nr	= X86_TRAP_PF;
 
 #ifdef CONFIG_MEMORY_FAILURE
 	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
@@ -851,23 +871,15 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 	force_sig_info_fault(SIGBUS, code, address, tsk, fault);
 }
 
-static noinline int
+static noinline void
 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 	       unsigned long address, unsigned int fault)
 {
-	/*
-	 * Pagefault was interrupted by SIGKILL. We have no reason to
-	 * continue pagefault.
-	 */
-	if (fatal_signal_pending(current)) {
-		if (!(fault & VM_FAULT_RETRY))
-			up_read(&current->mm->mmap_sem);
-		if (!(error_code & PF_USER))
-			no_context(regs, error_code, address, 0, 0);
-		return 1;
+	if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
+		up_read(&current->mm->mmap_sem);
+		no_context(regs, error_code, address, 0, 0);
+		return;
 	}
-	if (!(fault & VM_FAULT_ERROR))
-		return 0;
 
 	if (fault & VM_FAULT_OOM) {
 		/* Kernel mode? Handle exceptions or die: */
@@ -875,10 +887,17 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 			up_read(&current->mm->mmap_sem);
 			no_context(regs, error_code, address,
 				   SIGSEGV, SEGV_MAPERR);
-			return 1;
+			return;
 		}
 
-		out_of_memory(regs, error_code, address);
+		up_read(&current->mm->mmap_sem);
+
+		/*
+		 * We ran out of memory, call the OOM killer, and return the
+		 * userspace (which will retry the fault, or kill us if we got
+		 * oom-killed):
+		 */
+		pagefault_out_of_memory();
 	} else {
 		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
 			     VM_FAULT_HWPOISON_LARGE))
@@ -886,7 +905,6 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 		else
 			BUG();
 	}
-	return 1;
 }
 
 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
@@ -912,7 +930,7 @@ static int spurious_fault_check(unsigned long error_code, pte_t *pte)
  * There are no security implications to leaving a stale TLB when
  * increasing the permissions on a page.
  */
-static noinline __kprobes int
+static noinline int
 spurious_fault(unsigned long error_code, unsigned long address)
 {
 	pgd_t *pgd;
@@ -943,14 +961,8 @@ spurious_fault(unsigned long error_code, unsigned long address)
 	if (pmd_large(*pmd))
 		return spurious_fault_check(error_code, (pte_t *) pmd);
 
-	/*
-	 * Note: don't use pte_present() here, since it returns true
-	 * if the _PAGE_PROTNONE bit is set.  However, this aliases the
-	 * _PAGE_GLOBAL bit, which for kernel pages give false positives
-	 * when CONFIG_DEBUG_PAGEALLOC is used.
-	 */
 	pte = pte_offset_kernel(pmd, address);
-	if (!(pte_flags(*pte) & _PAGE_PRESENT))
+	if (!pte_present(*pte))
 		return 0;
 
 	ret = spurious_fault_check(error_code, pte);
@@ -966,6 +978,7 @@ spurious_fault(unsigned long error_code, unsigned long address)
 
 	return ret;
 }
+NOKPROBE_SYMBOL(spurious_fault);
 
 int show_unhandled_signals = 1;
 
@@ -995,29 +1008,45 @@ static int fault_in_kernel_space(unsigned long address)
 	return address >= TASK_SIZE_MAX;
 }
 
+static inline bool smap_violation(int error_code, struct pt_regs *regs)
+{
+	if (!IS_ENABLED(CONFIG_X86_SMAP))
+		return false;
+
+	if (!static_cpu_has(X86_FEATURE_SMAP))
+		return false;
+
+	if (error_code & PF_USER)
+		return false;
+
+	if (!user_mode_vm(regs) && (regs->flags & X86_EFLAGS_AC))
+		return false;
+
+	return true;
+}
+
 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
  * routines.
+ *
+ * This function must have noinline because both callers
+ * {,trace_}do_page_fault() have notrace on. Having this an actual function
+ * guarantees there's a function trace entry.
  */
-dotraplinkage void __kprobes
-do_page_fault(struct pt_regs *regs, unsigned long error_code)
+static noinline void
+__do_page_fault(struct pt_regs *regs, unsigned long error_code,
+		unsigned long address)
 {
 	struct vm_area_struct *vma;
 	struct task_struct *tsk;
-	unsigned long address;
 	struct mm_struct *mm;
 	int fault;
-	int write = error_code & PF_WRITE;
-	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
-					(write ? FAULT_FLAG_WRITE : 0);
+	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 	tsk = current;
 	mm = tsk->mm;
 
-	/* Get the faulting address: */
-	address = read_cr2();
-
 	/*
 	 * Detect and handle instructions that would cause a page fault for
 	 * both a tracked kernel page and a userspace page.
@@ -1056,7 +1085,7 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
 			return;
 
 		/* kprobes don't want to hook the spurious faults: */
-		if (notify_page_fault(regs))
+		if (kprobes_fault(regs))
 			return;
 		/*
 		 * Don't take the mm semaphore here. If we fixup a prefetch
@@ -1068,8 +1097,26 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	}
 
 	/* kprobes don't want to hook the spurious faults: */
-	if (unlikely(notify_page_fault(regs)))
+	if (unlikely(kprobes_fault(regs)))
 		return;
+
+	if (unlikely(error_code & PF_RSVD))
+		pgtable_bad(regs, error_code, address);
+
+	if (unlikely(smap_violation(error_code, regs))) {
+		bad_area_nosemaphore(regs, error_code, address);
+		return;
+	}
+
+	/*
+	 * If we're in an interrupt, have no user context or are running
+	 * in an atomic region then we must not take the fault:
+	 */
+	if (unlikely(in_atomic() || !mm)) {
+		bad_area_nosemaphore(regs, error_code, address);
+		return;
+	}
+
 	/*
 	 * It's safe to allow irq's after cr2 has been saved and the
 	 * vmalloc fault has been handled.
@@ -1080,24 +1127,16 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	if (user_mode_vm(regs)) {
 		local_irq_enable();
 		error_code |= PF_USER;
+		flags |= FAULT_FLAG_USER;
 	} else {
 		if (regs->flags & X86_EFLAGS_IF)
 			local_irq_enable();
 	}
 
-	if (unlikely(error_code & PF_RSVD))
-		pgtable_bad(regs, error_code, address);
-
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
-	/*
-	 * If we're in an interrupt, have no user context or are running
-	 * in an atomic region then we must not take the fault:
-	 */
-	if (unlikely(in_atomic() || !mm)) {
-		bad_area_nosemaphore(regs, error_code, address);
-		return;
-	}
+	if (error_code & PF_WRITE)
+		flags |= FAULT_FLAG_WRITE;
 
 	/*
 	 * When running in the kernel we expect faults to occur only to
@@ -1177,9 +1216,17 @@ good_area:
 	 */
 	fault = handle_mm_fault(mm, vma, address, flags);
 
-	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
-		if (mm_fault_error(regs, error_code, address, fault))
-			return;
+	/*
+	 * If we need to retry but a fatal signal is pending, handle the
+	 * signal first. We do not need to release the mmap_sem because it
+	 * would already be released in __lock_page_or_retry in mm/filemap.c.
+	 */
+	if (unlikely((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)))
+		return;
+
+	if (unlikely(fault & VM_FAULT_ERROR)) {
+		mm_fault_error(regs, error_code, address, fault);
+		return;
 	}
 
 	/*
@@ -1201,6 +1248,7 @@ good_area:
 			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 			 * of starvation. */
 			flags &= ~FAULT_FLAG_ALLOW_RETRY;
+			flags |= FAULT_FLAG_TRIED;
 			goto retry;
 		}
 	}
@@ -1209,3 +1257,55 @@ good_area:
 
 	up_read(&mm->mmap_sem);
 }
+NOKPROBE_SYMBOL(__do_page_fault);
+
+dotraplinkage void notrace
+do_page_fault(struct pt_regs *regs, unsigned long error_code)
+{
+	unsigned long address = read_cr2(); /* Get the faulting address */
+	enum ctx_state prev_state;
+
+	/*
+	 * We must have this function tagged with __kprobes, notrace and call
+	 * read_cr2() before calling anything else. To avoid calling any kind
+	 * of tracing machinery before we've observed the CR2 value.
+	 *
+	 * exception_{enter,exit}() contain all sorts of tracepoints.
+	 */
+
+	prev_state = exception_enter();
+	__do_page_fault(regs, error_code, address);
+	exception_exit(prev_state);
+}
+NOKPROBE_SYMBOL(do_page_fault);
+
+#ifdef CONFIG_TRACING
+static nokprobe_inline void
+trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
+			 unsigned long error_code)
+{
+	if (user_mode(regs))
+		trace_page_fault_user(address, regs, error_code);
+	else
+		trace_page_fault_kernel(address, regs, error_code);
+}
+
+dotraplinkage void notrace
+trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
+{
+	/*
+	 * The exception_enter and tracepoint processing could
+	 * trigger another page faults (user space callchain
+	 * reading) and destroy the original cr2 value, so read
+	 * the faulting address now.
+	 */
+	unsigned long address = read_cr2();
+	enum ctx_state prev_state;
+
+	prev_state = exception_enter();
+	trace_page_fault_entries(address, regs, error_code);
+	__do_page_fault(regs, error_code, address);
+	exception_exit(prev_state);
+}
+NOKPROBE_SYMBOL(trace_do_page_fault);
+#endif /* CONFIG_TRACING */