lkml.org 
[lkml]   [2018]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH v3 9/9] vfs, fdtable: prevent bounds-check bypass via speculative execution
From
Date
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@zeniv.linux.org.uk>
Co-developed-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.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;
}

\
 
 \ /
  Last update: 2018-01-14 23:26    [W:0.101 / U:0.272 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site