From: Andy Lutomirski <[email protected]>

The comment suggests that show_stack(NULL, NULL) should backtrace the
current context, but the code doesn't match the comment. If regs are
given, start the "Stack:" hexdump at regs->sp.

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: 
http://lkml.kernel.org/r/efcd79bf4106d61f1cd258c2caa87f3a0618eeac.1466036668.git.l...@kernel.org
Signed-off-by: Borislav Petkov <[email protected]>
---
 arch/x86/kernel/dumpstack_32.c | 4 +++-
 arch/x86/kernel/dumpstack_64.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 464ffd69b92e..91069ebe3c87 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -98,7 +98,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs 
*regs,
        int i;
 
        if (sp == NULL) {
-               if (task)
+               if (regs)
+                       sp = (unsigned long *)regs->sp;
+               else if (task)
                        sp = (unsigned long *)task->thread.sp;
                else
                        sp = (unsigned long *)&sp;
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 5f1c6266eb30..603356a5597a 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -266,7 +266,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs 
*regs,
         * back trace for this cpu:
         */
        if (sp == NULL) {
-               if (task)
+               if (regs)
+                       sp = (unsigned long *)regs->sp;
+               else if (task)
                        sp = (unsigned long *)task->thread.sp;
                else
                        sp = (unsigned long *)&sp;
-- 
2.8.4

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