fs: prevent speculative execution

CVE-2017-5753
CVE-2017-5715

Real commit text tbd

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
(cherry picked from commit 8a0f2aeaa333f5c4e41b5d366745015fa855232f)
Signed-off-by: Andy Whitcroft <apw@canonical.com>

diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 5295535b60c60768ccb91034b3ba290dc1a57f1a..4f2c526d568385a28e9276a175e2c037a72ecff8 100644 (file)
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -81,8 +81,10 @@ static inline struct file *__fcheck_files(struct files_struct *files, unsigned i
 {
        struct fdtable *fdt = rcu_dereference_raw(files->fdt);
 
-       if (fd < fdt->max_fds)
+       if (fd < fdt->max_fds) {
+               gmb();
                return rcu_dereference_raw(fdt->fd[fd]);
+       }
        return NULL;
 }