Merge 5.7-rc3 into android-mainline

Linux 5.7-rc3

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I7ac2896e866a898b1f42fc8fd6d60b40a75ae1f0

mm/madvise.c

@@ -27,6 +27,7 @@
 #include <linux/swapops.h>
 #include <linux/shmem_fs.h>
 #include <linux/mmu_notifier.h>
+#include <linux/sched/mm.h>
 
 #include <asm/tlb.h>
 
@@ -1090,6 +1091,23 @@ int do_madvise(unsigned long start, size_t len_in, int behavior)
 	if (write) {
 		if (down_write_killable(&current->mm->mmap_sem))
 			return -EINTR;
+
+		/*
+		 * We may have stolen the mm from another process
+		 * that is undergoing core dumping.
+		 *
+		 * Right now that's io_ring, in the future it may
+		 * be remote process management and not "current"
+		 * at all.
+		 *
+		 * We need to fix core dumping to not do this,
+		 * but for now we have the mmget_still_valid()
+		 * model.
+		 */
+		if (!mmget_still_valid(current->mm)) {
+			up_write(&current->mm->mmap_sem);
+			return -EINTR;
+		}
 	} else {
 		down_read(&current->mm->mmap_sem);
 	}