[PATCH v3 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS

Andy Lutomirski
2016-06-20T23:45:17Z

If we overflow the stack into a guard page, we'll recursively fault
when trying to dump the contents of the guard page. Use
probe_kernel_address so we can recover if this happens.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/kernel/dumpstack_64.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 603356a5597a..5e298638c790 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -276,6 +276,8 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,

stack = sp;
for (i = 0; i < kstack_depth_to_print; i++) {
+ unsigned long word;
+
if (stack >= irq_stack && stack <= irq_stack_end) {
if (stack == irq_stack_end) {
stack = (unsigned long *) (irq_stack_end[-1]);
@@ -285,12 +287,18 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
if (kstack_end(stack))
break;
}
+
+ if (probe_kernel_address(stack, word))
+ break;
+
if ((i % STACKSLOTS_PER_LINE) == 0) {
if (i != 0)
pr_cont("\n");
- printk("%s %016lx", log_lvl, *stack++);
+ printk("%s %016lx", log_lvl, word);
} else
- pr_cont(" %016lx", *stack++);
+ pr_cont(" %016lx", word);
+
+ stack++;
touch_nmi_watchdog();
}
preempt_enable();
--
2.5.5