uprobes: __create_xol_area() must nullify xol_mapping.fault
authorOleg Nesterov <oleg@redhat.com>
Sat, 27 Feb 2016 22:11:28 +0000 (23:11 +0100)
committerIngo Molnar <mingo@kernel.org>
Mon, 29 Feb 2016 07:47:51 +0000 (08:47 +0100)
As Jiri pointed out, this 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.

Suggested-by: Jiri Olsa <jolsa@redhat.com>
Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <tipbot@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Anand <panand@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160227221128.GA29565@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/events/uprobes.c

index 0167679..5f6ce93 100644 (file)
@@ -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;
        area->pages[0] = alloc_page(GFP_HIGHUSER);
        if (!area->pages[0])