Merge tag 'v4.19.59-rt24' into toradex_4.19.y-rttoradex_4.19.y-rt

Linux 4.19.59-rt24

1 files changed, 9 insertions, 0 deletions

diff --git a/kernel/cred.c b/kernel/cred.c
index ecf03657e71c..efd04b2ec84c 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -448,6 +448,15 @@ int commit_creds(struct cred *new)
 		if (task->mm)
 			set_dumpable(task->mm, suid_dumpable);
 		task->pdeath_signal = 0;
+		/*
+		 * If a task drops privileges and becomes nondumpable,
+		 * the dumpability change must become visible before
+		 * the credential change; otherwise, a __ptrace_may_access()
+		 * racing with this change may be able to attach to a task it
+		 * shouldn't be able to attach to (as if the task had dropped
+		 * privileges without becoming nondumpable).
+		 * Pairs with a read barrier in __ptrace_may_access().
+		 */
 		smp_wmb();
 	}