Merge remote-tracking branch 'origin/master' into perf/core

Further perf/core patches will depend on:

  d3f7b1bb2040 ("mm/gup: fix gup_fast with dynamic page table folding")

which is already in Linus' tree.

1 files changed, 23 insertions, 6 deletions

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 48ce44576947..97aa900386cb 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -29,8 +29,8 @@ static int die_counter;
 
 static struct pt_regs exec_summary_regs;
 
-bool in_task_stack(unsigned long *stack, struct task_struct *task,
-		   struct stack_info *info)
+bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task,
+			   struct stack_info *info)
 {
 	unsigned long *begin = task_stack_page(task);
 	unsigned long *end   = task_stack_page(task) + THREAD_SIZE;
@@ -46,7 +46,8 @@ bool in_task_stack(unsigned long *stack, struct task_struct *task,
 	return true;
 }
 
-bool in_entry_stack(unsigned long *stack, struct stack_info *info)
+/* Called from get_stack_info_noinstr - so must be noinstr too */
+bool noinstr in_entry_stack(unsigned long *stack, struct stack_info *info)
 {
 	struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
 
@@ -77,6 +78,9 @@ static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src,
 	if (!user_mode(regs))
 		return copy_from_kernel_nofault(buf, (u8 *)src, nbytes);
 
+	/* The user space code from other tasks cannot be accessed. */
+	if (regs != task_pt_regs(current))
+		return -EPERM;
 	/*
 	 * Make sure userspace isn't trying to trick us into dumping kernel
 	 * memory by pointing the userspace instruction pointer at it.
@@ -84,6 +88,12 @@ static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src,
 	if (__chk_range_not_ok(src, nbytes, TASK_SIZE_MAX))
 		return -EINVAL;
 
+	/*
+	 * Even if named copy_from_user_nmi() this can be invoked from
+	 * other contexts and will not try to resolve a pagefault, which is
+	 * the correct thing to do here as this code can be called from any
+	 * context.
+	 */
 	return copy_from_user_nmi(buf, (void __user *)src, nbytes);
 }
 
@@ -114,12 +124,19 @@ void show_opcodes(struct pt_regs *regs, const char *loglvl)
 	u8 opcodes[OPCODE_BUFSIZE];
 	unsigned long prologue = regs->ip - PROLOGUE_SIZE;
 
-	if (copy_code(regs, opcodes, prologue, sizeof(opcodes))) {
-		printk("%sCode: Bad RIP value.\n", loglvl);
-	} else {
+	switch (copy_code(regs, opcodes, prologue, sizeof(opcodes))) {
+	case 0:
 		printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"
 		       __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,
 		       opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);
+		break;
+	case -EPERM:
+		/* No access to the user space stack of other tasks. Ignore. */
+		break;
+	default:
+		printk("%sCode: Unable to access opcode bytes at RIP 0x%lx.\n",
+		       loglvl, prologue);
+		break;
 	}
 }