[tip:x86/urgent] x86/unwind: Align stack pointer in unwinder dump

[tip-bot for Josh Poimboeuf]

Commit-ID:  99bd28a49b150e4b938313a63b5532d95ba77885
Gitweb:     https://git.kernel.org/tip/99bd28a49b150e4b938313a63b5532d95ba77885
Author:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Mon, 9 Oct 2017 20:20:04 -0500
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 10 Oct 2017 12:49:49 +0200

x86/unwind: Align stack pointer in unwinder dump

When printing the unwinder dump, the stack pointer could be unaligned,
for one of two reasons:

- stack corruption; or

- GCC created an unaligned stack.

There's no way for the unwinder to tell the difference between the two,
so we have to assume one or the other.  GCC unaligned stacks are very
rare, and have only been spotted before GCC 5.  Presumably, if we're
doing an unwinder stack dump, stack corruption is more likely than a
GCC unaligned stack.  So always align the stack before starting the
dump.

Reported-and-tested-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reported-and-tested-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Byungchul Park <byungchul.park@xxxxxxx>
Cc: LKP <lkp@xxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/2f540c515946ab09ed267e1a1d6421202a0cce08.1507597785.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/unwind_frame.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 4949bbc..81aca07 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -44,7 +44,8 @@ static void unwind_dump(struct unwind_state *state)
 			state->stack_info.type, state->stack_info.next_sp,
 			state->stack_mask, state->graph_idx);
 
-	for (sp = state->orig_sp; sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
+	for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
+	     sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
 		if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
 			break;