mm, oom: fix potential data corruption when oom_reaper races with writer

[karo-tx-linux.git] / include / linux / oom.h

diff --git a/include/linux/oom.h b/include/linux/oom.h
index 8a266e2be5a63a29a2de38ff76f0bdc2e4fac08e..76aac4ce39bcf59e2e5eeb38053cf05f0c9d05ae 100644 (file)
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -6,6 +6,8 @@
 #include <linux/types.h>
 #include <linux/nodemask.h>
 #include <uapi/linux/oom.h>
+#include <linux/sched/coredump.h> /* MMF_* */
+#include <linux/mm.h> /* VM_FAULT* */
 
 struct zonelist;
 struct notifier_block;
@@ -63,6 +65,26 @@ static inline bool tsk_is_oom_victim(struct task_struct * tsk)
        return tsk->signal->oom_mm;
 }
 
+/*
+ * Checks whether a page fault on the given mm is still reliable.
+ * This is no longer true if the oom reaper started to reap the
+ * address space which is reflected by MMF_UNSTABLE flag set in
+ * the mm. At that moment any !shared mapping would lose the content
+ * and could cause a memory corruption (zero pages instead of the
+ * original content).
+ *
+ * User should call this before establishing a page table entry for
+ * a !shared mapping and under the proper page table lock.
+ *
+ * Return 0 when the PF is safe VM_FAULT_SIGBUS otherwise.
+ */
+static inline int check_stable_address_space(struct mm_struct *mm)
+{
+       if (unlikely(test_bit(MMF_UNSTABLE, &mm->flags)))
+               return VM_FAULT_SIGBUS;
+       return 0;
+}
+
 extern unsigned long oom_badness(struct task_struct *p,
                struct mem_cgroup *memcg, const nodemask_t *nodemask,
                unsigned long totalpages);