[PATCH 3.2 083/101] mm/mempolicy.c: fix error handling in set_mempolicy and mbind.

[Ben Hutchings]

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

------------------

From: Chris Salls <sa...@cs.ucsb.edu>

commit cf01fb9985e8deb25ccf0ea54d916b8871ae0e62 upstream.

In the case that compat_get_bitmap fails we do not want to copy the
bitmap to the user as it will contain uninitialized stack data and leak
sensitive data.

Signed-off-by: Chris Salls <sa...@cs.ucsb.edu>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 mm/mempolicy.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1446,7 +1446,6 @@ asmlinkage long compat_sys_get_mempolicy
 asmlinkage long compat_sys_set_mempolicy(int mode, compat_ulong_t __user 
*nmask,
                                     compat_ulong_t maxnode)
 {
-       long err = 0;
        unsigned long __user *nm = NULL;
        unsigned long nr_bits, alloc_size;
        DECLARE_BITMAP(bm, MAX_NUMNODES);
@@ -1455,14 +1454,13 @@ asmlinkage long compat_sys_set_mempolicy
        alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
 
        if (nmask) {
-               err = compat_get_bitmap(bm, nmask, nr_bits);
+               if (compat_get_bitmap(bm, nmask, nr_bits))
+                       return -EFAULT;
                nm = compat_alloc_user_space(alloc_size);
-               err |= copy_to_user(nm, bm, alloc_size);
+               if (copy_to_user(nm, bm, alloc_size))
+                       return -EFAULT;
        }
 
-       if (err)
-               return -EFAULT;
-
        return sys_set_mempolicy(mode, nm, nr_bits+1);
 }
 
@@ -1470,7 +1468,6 @@ asmlinkage long compat_sys_mbind(compat_
                             compat_ulong_t mode, compat_ulong_t __user *nmask,
                             compat_ulong_t maxnode, compat_ulong_t flags)
 {
-       long err = 0;
        unsigned long __user *nm = NULL;
        unsigned long nr_bits, alloc_size;
        nodemask_t bm;
@@ -1479,14 +1476,13 @@ asmlinkage long compat_sys_mbind(compat_
        alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
 
        if (nmask) {
-               err = compat_get_bitmap(nodes_addr(bm), nmask, nr_bits);
+               if (compat_get_bitmap(nodes_addr(bm), nmask, nr_bits))
+                       return -EFAULT;
                nm = compat_alloc_user_space(alloc_size);
-               err |= copy_to_user(nm, nodes_addr(bm), alloc_size);
+               if (copy_to_user(nm, nodes_addr(bm), alloc_size))
+                       return -EFAULT;
        }
 
-       if (err)
-               return -EFAULT;
-
        return sys_mbind(start, len, mode, nm, nr_bits+1, flags);
 }