[PATCH 3.10 228/268] mm/mempolicy.c: fix error handling in set_mempolicy and mbind.

Willy Tarreau
2017-06-19T19:16:47Z

From: Chris Salls <salls@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 <salls@cs.ucsb.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
mm/mempolicy.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index b2061bb..e57c967 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1537,7 +1537,6 @@ asmlinkage long compat_sys_get_mempolicy(int __user *policy,
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);
@@ -1546,14 +1545,13 @@ asmlinkage long compat_sys_set_mempolicy(int mode, compat_ulong_t __user *nmask,
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);
}

@@ -1561,7 +1559,6 @@ asmlinkage long compat_sys_mbind(compat_ulong_t start, compat_ulong_t len,
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;
@@ -1570,14 +1567,13 @@ asmlinkage long compat_sys_mbind(compat_ulong_t start, compat_ulong_t len,
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);
}

--
2.8.0.rc2.1.gbe9624a