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Message-ID: <151703976200.26578.16181908340589076165.stgit@dwillia2-desk3.amr.corp.intel.com>
Date: Fri, 26 Jan 2018 23:56:02 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: tglx@...utronix.de
Cc: linux-arch@...r.kernel.org, kernel-hardening@...ts.openwall.com,
gregkh@...uxfoundation.org, Al Viro <viro@...iv.linux.org.uk>,
torvalds@...ux-foundation.org, alan@...ux.intel.com
Subject: [PATCH v5 09/12] vfs,
fdtable: prevent bounds-check bypass via speculative execution
'fd' is a user controlled value that is used as a data dependency to
read from the 'fdt->fd' array. In order to avoid potential leaks of
kernel memory values, block speculative execution of the instruction
stream that could issue reads based on an invalid 'file *' returned from
__fcheck_files.
Cc: Al Viro <viro@...iv.linux.org.uk>
Co-developed-by: Elena Reshetova <elena.reshetova@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
include/linux/fdtable.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 1c65817673db..c61f06c77fdf 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -10,6 +10,7 @@
#include <linux/compiler.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
+#include <linux/nospec.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/fs.h>
@@ -82,8 +83,10 @@ 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) {
+ fd = array_idx(fd, fdt->max_fds);
return rcu_dereference_raw(fdt->fd[fd]);
+ }
return NULL;
}
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