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Message-ID: <151586749581.5820.10884753209923259828.stgit@dwillia2-desk3.amr.corp.intel.com>
Date: Sat, 13 Jan 2018 10:18:16 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: linux-kernel@...r.kernel.org
Cc: linux-arch@...r.kernel.org, kernel-hardening@...ts.openwall.com,
gregkh@...uxfoundation.org, Al Viro <viro@...iv.linux.org.uk>,
tglx@...utronix.de, torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
alan@...ux.intel.com
Subject: [PATCH v3 9/9] vfs,
fdtable: prevent bounds-check bypass via speculative execution
Expectedly, static analysis reports that '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 | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 1c65817673db..9731f1a255db 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>
@@ -81,9 +82,11 @@ struct dentry;
static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
{
struct fdtable *fdt = rcu_dereference_raw(files->fdt);
+ struct file __rcu **fdp;
- if (fd < fdt->max_fds)
- return rcu_dereference_raw(fdt->fd[fd]);
+ fdp = array_ptr(fdt->fd, fd, fdt->max_fds);
+ if (fdp)
+ return rcu_dereference_raw(*fdp);
return NULL;
}
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