From 8661e7a75b2aa789797f46668ff8c3e885bc5710 Mon Sep 17 00:00:00 2001 From: Elena Reshetova <elena.reshetova@intel.com> Date: Wed, 30 Aug 2017 13:52:22 +0300 Subject: [PATCH] fs: prevent speculative execution CVE-2017-5753 (Spectre v1 Intel) Since the fd value in function __fcheck_files() seems to be controllable by userspace and later on conditionally (upon bound check) used to resolve fdt->fd, insert an observable speculation barrier before its usage. This should prevent observable speculation on that branch and avoid kernel memory leak. Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> Signed-off-by: Andy Whitcroft <apw@canonical.com> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> --- include/linux/fdtable.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 5295535b60c6..9492255463cb 100644 --- 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) { + osb(); return rcu_dereference_raw(fdt->fd[fd]); + } return NULL; } -- 2.30.9