shared_policy_replace() use of sp_alloc() is unsafe. 1) sp_node cannot
be dereferenced if sp->lock is not held and 2) another thread can modify
sp_node between spin_unlock for allocating a new sp node and next
spin_lock. The bug was introduced before 2.6.12-rc2.
Kosaki's original patch for this problem was to allocate an sp node and
policy within shared_policy_replace and initialise it when the lock is
reacquired. I was not keen on this approach because it partially
duplicates sp_alloc(). As the paths were sp->lock is taken are not that
performance critical this patch converts sp->lock to sp->mutex so it can
sleep when calling sp_alloc().
[kosaki.motohiro@jp.fujitsu.com: Original patch]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Cc: Josh Boyer <jwboyer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
struct shared_policy {
struct rb_root root;
struct shared_policy {
struct rb_root root;
};
void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol);
};
void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol);
*/
/* lookup first element intersecting start-end */
*/
/* lookup first element intersecting start-end */
-/* Caller holds sp->lock */
+/* Caller holds sp->mutex */
static struct sp_node *
sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
{
static struct sp_node *
sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
{
if (!sp->root.rb_node)
return NULL;
if (!sp->root.rb_node)
return NULL;
+ mutex_lock(&sp->mutex);
sn = sp_lookup(sp, idx, idx+1);
if (sn) {
mpol_get(sn->policy);
pol = sn->policy;
}
sn = sp_lookup(sp, idx, idx+1);
if (sn) {
mpol_get(sn->policy);
pol = sn->policy;
}
- spin_unlock(&sp->lock);
+ mutex_unlock(&sp->mutex);
static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
unsigned long end, struct sp_node *new)
{
static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
unsigned long end, struct sp_node *new)
{
- struct sp_node *n, *new2 = NULL;
+ struct sp_node *n;
+ int ret = 0;
-restart:
- spin_lock(&sp->lock);
+ mutex_lock(&sp->mutex);
n = sp_lookup(sp, start, end);
/* Take care of old policies in the same range. */
while (n && n->start < end) {
n = sp_lookup(sp, start, end);
/* Take care of old policies in the same range. */
while (n && n->start < end) {
} else {
/* Old policy spanning whole new range. */
if (n->end > end) {
} else {
/* Old policy spanning whole new range. */
if (n->end > end) {
+ struct sp_node *new2;
+ new2 = sp_alloc(end, n->end, n->policy);
- spin_unlock(&sp->lock);
- new2 = sp_alloc(end, n->end, n->policy);
- if (!new2)
- return -ENOMEM;
- goto restart;
+ ret = -ENOMEM;
+ goto out;
}
n->end = start;
sp_insert(sp, new2);
}
n->end = start;
sp_insert(sp, new2);
break;
} else
n->end = start;
break;
} else
n->end = start;
}
if (new)
sp_insert(sp, new);
}
if (new)
sp_insert(sp, new);
- spin_unlock(&sp->lock);
- if (new2) {
- mpol_put(new2->policy);
- kmem_cache_free(sn_cache, new2);
- }
- return 0;
+out:
+ mutex_unlock(&sp->mutex);
+ return ret;
int ret;
sp->root = RB_ROOT; /* empty tree == default mempolicy */
int ret;
sp->root = RB_ROOT; /* empty tree == default mempolicy */
- spin_lock_init(&sp->lock);
+ mutex_init(&sp->mutex);
if (mpol) {
struct vm_area_struct pvma;
if (mpol) {
struct vm_area_struct pvma;
if (!p->root.rb_node)
return;
if (!p->root.rb_node)
return;
next = rb_first(&p->root);
while (next) {
n = rb_entry(next, struct sp_node, nd);
next = rb_first(&p->root);
while (next) {
n = rb_entry(next, struct sp_node, nd);
mpol_put(n->policy);
kmem_cache_free(sn_cache, n);
}
mpol_put(n->policy);
kmem_cache_free(sn_cache, n);
}
+ mutex_unlock(&p->mutex);
}
/* assumes fs == KERNEL_DS */
}
/* assumes fs == KERNEL_DS */