diff mbox

[stable,4.4,16/29] vfs, fdtable: Prevent bounds-check bypass via speculative execution

Message ID 1519382538-15143-17-git-send-email-jinpu.wangl@profitbricks.com (mailing list archive)
State New, archived
Headers show

Commit Message

Jinpu Wang Feb. 23, 2018, 10:42 a.m. UTC 
From: Dan Williams <dan.j.williams@intel.com>

(cherry picked from commit 56c30ba7b348b90484969054d561f711ba196507)

'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@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: kernel-hardening@lists.openwall.com
Cc: gregkh@linuxfoundation.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: torvalds@linux-foundation.org
Cc: alan@linux.intel.com
Link: https://lkml.kernel.org/r/151727418500.33451.17392199002892248656.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[jwang: cherry pick to 4.4]
Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
---
 include/linux/fdtable.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
diff mbox

Patch

diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 5295535..a7b7a05 100644
--- 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>
@@ -81,8 +82,10 @@  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_index_nospec(fd, fdt->max_fds);
 		return rcu_dereference_raw(fdt->fd[fd]);
+	}
 	return NULL;
 }