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-rw-r--r--fs/open.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/fs/open.c b/fs/open.c
index b5b80469b93d..a59abe3c669a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -374,6 +374,25 @@ long do_faccessat(int dfd, const char __user *filename, int mode)
override_cred->cap_permitted;
}
+ /*
+ * The new set of credentials can *only* be used in
+ * task-synchronous circumstances, and does not need
+ * RCU freeing, unless somebody then takes a separate
+ * reference to it.
+ *
+ * NOTE! This is _only_ true because this credential
+ * is used purely for override_creds() that installs
+ * it as the subjective cred. Other threads will be
+ * accessing ->real_cred, not the subjective cred.
+ *
+ * If somebody _does_ make a copy of this (using the
+ * 'get_current_cred()' function), that will clear the
+ * non_rcu field, because now that other user may be
+ * expecting RCU freeing. But normal thread-synchronous
+ * cred accesses will keep things non-RCY.
+ */
+ override_cred->non_rcu = 1;
+
old_cred = override_creds(override_cred);
retry:
res = user_path_at(dfd, filename, lookup_flags, &path);