On 6/27/19 5:32 PM, Doug Berger wrote:
A timing hazard exists when an early fork/exec thread begins exiting and sets its mm pointer to NULL while a separate core tries to update the section information.This commit ensures that the mm pointer is not NULL before setting its section parameters. The arguments provided by commit 11ce4b33aedc ("ARM: 8672/1: mm: remove tasklist locking from update_sections_early()") are equally valid for not requiring grabbing the task_lock around this check. Fixes: 08925c2f124f ("ARM: 8464/1: Update all mm structures with section adjustments") Signed-off-by: Doug Berger <open...@gmail.com> --- arch/arm/mm/init.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c index be0b42937888..bdc70dff477b 100644 --- a/arch/arm/mm/init.c +++ b/arch/arm/mm/init.c @@ -616,7 +616,8 @@ static void update_sections_early(struct section_perm perms[], int n) if (t->flags & PF_KTHREAD) continue; for_each_thread(t, s) - set_section_perms(perms, n, true, s->mm); + if (s->mm) + set_section_perms(perms, n, true, s->mm); } set_section_perms(perms, n, true, current->active_mm); set_section_perms(perms, n, true, &init_mm);
Acked-by: Laura Abbott <labb...@redhat.com>
