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Message-ID: <lsq.1520823814.357571797@decadent.org.uk>
Date: Mon, 12 Mar 2018 03:03:34 +0000
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org, linux-arch@...r.kernel.org,
"Al Viro" <viro@...iv.linux.org.uk>,
gregkh@...uxfoundation.org,
"Thomas Gleixner" <tglx@...utronix.de>,
"Dan Williams" <dan.j.williams@...el.com>,
torvalds@...ux-foundation.org, kernel-hardening@...ts.openwall.com,
alan@...ux.intel.com
Subject: [PATCH 3.2 088/104] vfs, fdtable: Prevent bounds-check bypass via
speculative execution
3.2.101-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Dan Williams <dan.j.williams@...el.com>
commit 56c30ba7b348b90484969054d561f711ba196507 upstream.
'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.
Co-developed-by: Elena Reshetova <elena.reshetova@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-arch@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com
Cc: gregkh@...uxfoundation.org
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: torvalds@...ux-foundation.org
Cc: alan@...ux.intel.com
Link: https://lkml.kernel.org/r/151727418500.33451.17392199002892248656.stgit@dwillia2-desk3.amr.corp.intel.com
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
include/linux/fdtable.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -9,6 +9,7 @@
#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>
@@ -85,8 +86,10 @@ static inline struct file * fcheck_files
struct file * file = NULL;
struct fdtable *fdt = files_fdtable(files);
- if (fd < fdt->max_fds)
+ if (fd < fdt->max_fds) {
+ fd = array_index_nospec(fd, fdt->max_fds);
file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
+ }
return file;
}
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