Messages in this thread | | | Date | Wed, 12 Oct 2016 12:41:18 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] mm: kmemleak: Ensure that the task stack is not freed during scanning |
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On Wed 12-10-16 10:57:03, Catalin Marinas wrote: > Commit 68f24b08ee89 ("sched/core: Free the stack early if > CONFIG_THREAD_INFO_IN_TASK") may cause the task->stack to be freed > during kmemleak_scan() execution, leading to either a NULL pointer > fault (if task->stack is NULL) or kmemleak accessing already freed > memory. This patch uses the new try_get_task_stack() API to ensure that > the task stack is not freed during kmemleak stack scanning.
Looks good to me
> Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: CAI Qian <caiqian@redhat.com> > Reported-by: CAI Qian <caiqian@redhat.com> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
> --- > > This was reported in a subsequent comment here: > > https://bugzilla.kernel.org/show_bug.cgi?id=173901 > > However, the original bugzilla entry doesn't look related to task stack > freeing as it was first reported on 4.8-rc8. Andy, sorry for cc'ing you > to bugzilla, please feel free to remove your email from the bug above (I > can't seem to be able to do it). > > mm/kmemleak.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index a5e453cf05c4..e5355a5b423f 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -1453,8 +1453,11 @@ static void kmemleak_scan(void) > > read_lock(&tasklist_lock); > do_each_thread(g, p) { > - scan_block(task_stack_page(p), task_stack_page(p) + > - THREAD_SIZE, NULL); > + void *stack = try_get_task_stack(p); > + if (stack) { > + scan_block(stack, stack + THREAD_SIZE, NULL); > + put_task_stack(p); > + } > } while_each_thread(g, p); > read_unlock(&tasklist_lock); > } > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
-- Michal Hocko SUSE Labs
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