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mm/mempolicy.c: fix error handling in set_mempolicy and mbind.

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.

Change-Id: I9dc15840515b7f61adef8cfc238e25dec0715860
Signed-off-by: Chris Salls <salls@cs.ucsb.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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salls authored and andi34 committed Apr 8, 2017
1 parent a8212d6 commit d4afaa7417bbe240bc39ab8f8b297db738baa9f9
Showing with 8 additions and 12 deletions.
  1. +8 −12 mm/mempolicy.c
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@@ -1439,7 +1439,6 @@ 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);
@@ -1448,22 +1447,20 @@ 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);
}
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;
@@ -1472,14 +1469,13 @@ 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);
}

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