3.2.101-rc1 review patch.  If anyone has any objections, please let me know.


From: Dan Williams <dan.j.willi...@intel.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

Co-developed-by: Elena Reshetova <elena.reshet...@intel.com>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: linux-a...@vger.kernel.org
Cc: kernel-harden...@lists.openwall.com
Cc: gre...@linuxfoundation.org
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: torva...@linux-foundation.org
Cc: a...@linux.intel.com
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <b...@decadent.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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