Messages in this thread | | | Date | Mon, 29 Feb 2016 12:42:10 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH tip/x86/asm] uprobes: __create_xol_area() must nullify xol_mapping.fault |
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On Sat, Feb 27, 2016 at 11:11:28PM +0100, Oleg Nesterov wrote: > As Jiri pointed out, the recent commit f872f5400cc0 "mm: Add a > vm_special_mapping.fault() method" breaks uprobes. __create_xol_area() > doesn't initialize the new ->fault() method and this obviously leads to > kernel crash when the application tries to execute the probed insn after > bp hit. > > We probably want to add uprobes_special_mapping_fault(), this allows to > turn xol_area->xol_mapping into a single instance of vm_special_mapping. > But we need a simple fix, so lets change __create_xol() to nullify the > new member as Jiri suggests. > > Reported-by: Jiri Olsa <jolsa@redhat.com> > Suggested-by: Jiri Olsa <jolsa@redhat.com> > Signed-off-by: Oleg Nesterov <oleg@redhat.com> > --- > kernel/events/uprobes.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 0167679..5f6ce93 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -1178,6 +1178,7 @@ static struct xol_area *__create_xol_area(unsigned long vaddr) > goto free_area; > > area->xol_mapping.name = "[uprobes]"; > + area->xol_mapping.fault = NULL; > area->xol_mapping.pages = area->pages;
Would not something like:
area->xol_mapping = (struct vm_special_mapping){ .name = "[uprobes]", .pages = area->pages, };
Be a more robust approach? That way, if someone adds more fields, they at least get initialized (to 0).
> area->pages[0] = alloc_page(GFP_HIGHUSER); > if (!area->pages[0])
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