x86: Fix dumpstack_64 to keep state of "used" variable in loop

Commit 2223f6f6eeaa "x86: Clean up dumpstack_64.c code" moved the used
variable to a local within the loop, but the in_exception_stack()
depended on being non-volatile with the ability to change it.

By always re-initializing the "used" variable to zero, it would cause
the in_exception_stack() to return the same thing each time, and
cause the dump_stack loop to go into an infinite loop.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 346b1df2412e238a35a558f66ec2b210b4710bf7..74c262a9b9f1d45f48361cf5b6d44eb1ea4520c4 100644 (file)
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -115,19 +115,18 @@ enum stack_type {
 };
 
 static enum stack_type
-analyze_stack(int cpu, struct task_struct *task,
-             unsigned long *stack, unsigned long **stack_end, char **id)
+analyze_stack(int cpu, struct task_struct *task, unsigned long *stack,
+             unsigned long **stack_end, unsigned *used, char **id)
 {
        unsigned long *irq_stack;
        unsigned long addr;
-       unsigned used = 0;
 
        addr = ((unsigned long)stack & (~(THREAD_SIZE - 1)));
        if ((unsigned long)task_stack_page(task) == addr)
                return STACK_IS_NORMAL;
 
        *stack_end = in_exception_stack(cpu, (unsigned long)stack,
-                                        &used, id);
+                                       used, id);
        if (*stack_end)
                return STACK_IS_EXCEPTION;
 
@@ -158,6 +157,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
        struct thread_info *tinfo;
        unsigned long *irq_stack;
        unsigned long dummy;
+       unsigned used = 0;
        int graph = 0;
        int done = 0;
 
@@ -186,7 +186,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                enum stack_type stype;
                char *id;
 
-               stype = analyze_stack(cpu, task, stack, &stack_end, &id);
+               stype = analyze_stack(cpu, task, stack, &stack_end, &used, &id);
 
                /* Default finish unless specified to continue */
                done = 1;