Re: [4.14-rc1 x86] WARNING: kernel stack regs at f60bbb12 in swapper:1 has bad 'bp' value 0ba00000

[Josh Poimboeuf]

On Tue, Oct 03, 2017 at 12:37:44PM +0200, Borislav Petkov wrote:
> On Tue, Oct 03, 2017 at 07:29:36PM +0900, Tetsuo Handa wrote:
> > Tetsuo Handa wrote:
> > > Tetsuo Handa wrote:
> > > > Tetsuo Handa wrote:
> > > > > I'm seeing below error between
> > > > > 4898b99c261efe32 ("Merge tag 'acpi-4.13-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm") (git bisect good (presumably))
> > > > > e6f3faa734a00c60 ("locking/lockdep: Fix workqueue crossrelease annotation") (git bisect bad) on linux.git .
> > > > 
> > > > F.Y.I. This error remains as of 46c1e79fee417f15 ("Merge branch 'perf-urgent-for-linus' of
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip") on linux.git .
> > > > 
> > > 
> > > This error still remains as of 6e80ecdddf4ea6f3 ("Merge branch 'libnvdimm-fixes'
> > > of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm") on linux.git .
> > > 
> > > I'm suspecting that this error is causing very unstable x86_32 kernel.
> > > It seems that this error occurs (though rare frequency) even on x86_64 kernel.
> > > 
> > > Nobody cares?
> > > 
> > 4.14-rc3 still trivially panics due to this error. Is this problem known?

Can you try with the following patch?  It should hopefully give more
useful information in the dump.

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index d145a0b1f529..191012762aa0 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;
 
@@ -178,7 +179,7 @@ static struct pt_regs *decode_frame_pointer(unsigned long *bp)
 {
 	unsigned long regs = (unsigned long)bp;
 
-	if (!(regs & 0x1))
+	if ((regs & (sizeof(long)-1)) != 1)
 		return NULL;
 
 	return (struct pt_regs *)(regs & ~0x1);
@@ -221,6 +222,10 @@ static bool update_stack_state(struct unwind_state *state,
 				   &state->stack_mask))
 			return false;
 
+	/* Make sure the frame pointer is properly aligned: */
+	if ((unsigned long)frame & (sizeof(long)-1))
+		return false;
+
 	/* Make sure it only unwinds up and doesn't overlap the prev frame: */
 	if (state->orig_sp && state->stack_info.type == prev_type &&
 	    frame < prev_frame_end)