Messages in this thread | | | From | Chunyan Zhang <> | Date | Tue, 21 Nov 2017 16:57:46 +0800 | Subject | Re: [PATCH] clk: fix a panic error caused by accessing NULL pointer |
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On 21 November 2017 at 03:12, Stephen Boyd <sboyd@codeaurora.org> wrote: > On 11/20, Chunyan Zhang wrote: >> From: Cai Li <cai.li@spreadtrum.com> >> >> In some cases the clock parent would be set NULL when doing re-parent, >> it will cause a NULL pointer accessing if clk_set trace event is enabled, >> since the trace event function would not check the input parameter. >> >> Signed-off-by: Cai Li <cai.li@spreadtrum.com> >> Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com> > > Fixes: tag? > >> --- >> drivers/clk/clk.c | 9 ++++----- >> 1 file changed, 4 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >> index c8d83ac..64efaf0 100644 >> --- a/drivers/clk/clk.c >> +++ b/drivers/clk/clk.c >> @@ -1242,13 +1242,12 @@ static int __clk_set_parent(struct clk_core *core, struct clk_core *parent, >> >> old_parent = __clk_set_parent_before(core, parent); >> >> - trace_clk_set_parent(core, parent); >> - >> /* change clock input source */ >> - if (parent && core->ops->set_parent) >> + if (parent && core->ops->set_parent) { >> + trace_clk_set_parent(core, parent); >> ret = core->ops->set_parent(core->hw, p_index); >> - >> - trace_clk_set_parent_complete(core, parent); >> + trace_clk_set_parent_complete(core, parent); >> + } > > Is the problem that parent may be NULL and the tracepoint > dereferences it?
Yes, I think that probably is uncommon usage though, it revealed that the tracepoint could be stronger :)
> Perhaps we need to update the tracepoint code > instead so that we always see that the tracepoint is called even > if we don't actually touch the hardware. Something like the patch > below instead.
Ok, we will cook a new patch according to your comments.
Thanks, Chunyan
> > ---8<---- > diff --git a/include/trace/events/clk.h b/include/trace/events/clk.h > index 758607226bfd..5a85ea2090c4 100644 > --- a/include/trace/events/clk.h > +++ b/include/trace/events/clk.h > @@ -139,7 +139,7 @@ DECLARE_EVENT_CLASS(clk_parent, > > TP_fast_assign( > __assign_str(name, core->name); > - __assign_str(pname, parent->name); > + __assign_str(pname, parent ? parent->name : NULL); > ), > > TP_printk("%s %s", __get_str(name), __get_str(pname)) > -- > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, > a Linux Foundation Collaborative Project
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