1 files changed, 48 insertions, 16 deletions

diff --git a/kernel/padata.c b/kernel/padata.c
index e3f639ff1670..7eee94166357 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -47,6 +47,22 @@ struct padata_mt_job_state {
 static void padata_free_pd(struct parallel_data *pd);
 static void __init padata_mt_helper(struct work_struct *work);
 
+static inline void padata_get_pd(struct parallel_data *pd)
+{
+	refcount_inc(&pd->refcnt);
+}
+
+static inline void padata_put_pd_cnt(struct parallel_data *pd, int cnt)
+{
+	if (refcount_sub_and_test(cnt, &pd->refcnt))
+		padata_free_pd(pd);
+}
+
+static inline void padata_put_pd(struct parallel_data *pd)
+{
+	padata_put_pd_cnt(pd, 1);
+}
+
 static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
 {
 	int cpu, target_cpu;
@@ -106,7 +122,7 @@ static int __init padata_work_alloc_mt(int nworks, void *data,
 {
 	int i;
 
-	spin_lock(&padata_works_lock);
+	spin_lock_bh(&padata_works_lock);
 	/* Start at 1 because the current task participates in the job. */
 	for (i = 1; i < nworks; ++i) {
 		struct padata_work *pw = padata_work_alloc();
@@ -116,7 +132,7 @@ static int __init padata_work_alloc_mt(int nworks, void *data,
 		padata_work_init(pw, padata_mt_helper, data, 0);
 		list_add(&pw->pw_list, head);
 	}
-	spin_unlock(&padata_works_lock);
+	spin_unlock_bh(&padata_works_lock);
 
 	return i;
 }
@@ -134,12 +150,12 @@ static void __init padata_works_free(struct list_head *works)
 	if (list_empty(works))
 		return;
 
-	spin_lock(&padata_works_lock);
+	spin_lock_bh(&padata_works_lock);
 	list_for_each_entry_safe(cur, next, works, pw_list) {
 		list_del(&cur->pw_list);
 		padata_work_free(cur);
 	}
-	spin_unlock(&padata_works_lock);
+	spin_unlock_bh(&padata_works_lock);
 }
 
 static void padata_parallel_worker(struct work_struct *parallel_work)
@@ -206,7 +222,7 @@ int padata_do_parallel(struct padata_shell *ps,
 	if ((pinst->flags & PADATA_RESET))
 		goto out;
 
-	refcount_inc(&pd->refcnt);
+	padata_get_pd(pd);
 	padata->pd = pd;
 	padata->cb_cpu = *cb_cpu;
 
@@ -274,7 +290,7 @@ static struct padata_priv *padata_find_next(struct parallel_data *pd,
 	if (remove_object) {
 		list_del_init(&padata->list);
 		++pd->processed;
-		pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false);
+		pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu);
 	}
 
 	spin_unlock(&reorder->lock);
@@ -336,8 +352,15 @@ static void padata_reorder(struct parallel_data *pd)
 	smp_mb();
 
 	reorder = per_cpu_ptr(pd->reorder_list, pd->cpu);
-	if (!list_empty(&reorder->list) && padata_find_next(pd, false))
-		queue_work(pinst->serial_wq, &pd->reorder_work);
+	if (!list_empty(&reorder->list) && padata_find_next(pd, false)) {
+		/*
+		 * Other context(eg. the padata_serial_worker) can finish the request.
+		 * To avoid UAF issue, add pd ref here, and put pd ref after reorder_work finish.
+		 */
+		padata_get_pd(pd);
+		if (!queue_work(pinst->serial_wq, &pd->reorder_work))
+			padata_put_pd(pd);
+	}
 }
 
 static void invoke_padata_reorder(struct work_struct *work)
@@ -348,6 +371,8 @@ static void invoke_padata_reorder(struct work_struct *work)
 	pd = container_of(work, struct parallel_data, reorder_work);
 	padata_reorder(pd);
 	local_bh_enable();
+	/* Pairs with putting the reorder_work in the serial_wq */
+	padata_put_pd(pd);
 }
 
 static void padata_serial_worker(struct work_struct *serial_work)
@@ -380,8 +405,7 @@ static void padata_serial_worker(struct work_struct *serial_work)
 	}
 	local_bh_enable();
 
-	if (refcount_sub_and_test(cnt, &pd->refcnt))
-		padata_free_pd(pd);
+	padata_put_pd_cnt(pd, cnt);
 }
 
 /**
@@ -404,7 +428,8 @@ void padata_do_serial(struct padata_priv *padata)
 	/* Sort in ascending order of sequence number. */
 	list_for_each_prev(pos, &reorder->list) {
 		cur = list_entry(pos, struct padata_priv, list);
-		if (cur->seq_nr < padata->seq_nr)
+		/* Compare by difference to consider integer wrap around */
+		if ((signed int)(cur->seq_nr - padata->seq_nr) < 0)
 			break;
 	}
 	list_add(&padata->list, pos);
@@ -512,9 +537,12 @@ void __init padata_do_multithreaded(struct padata_mt_job *job)
 	 * thread function.  Load balance large jobs between threads by
 	 * increasing the number of chunks, guarantee at least the minimum
 	 * chunk size from the caller, and honor the caller's alignment.
+	 * Ensure chunk_size is at least 1 to prevent divide-by-0
+	 * panic in padata_mt_helper().
 	 */
 	ps.chunk_size = job->size / (ps.nworks * load_balance_factor);
 	ps.chunk_size = max(ps.chunk_size, job->min_chunk);
+	ps.chunk_size = max(ps.chunk_size, 1ul);
 	ps.chunk_size = roundup(ps.chunk_size, job->align);
 
 	list_for_each_entry(pw, &works, pw_list)
@@ -677,8 +705,7 @@ static int padata_replace(struct padata_instance *pinst)
 	synchronize_rcu();
 
 	list_for_each_entry_continue_reverse(ps, &pinst->pslist, list)
-		if (refcount_dec_and_test(&ps->opd->refcnt))
-			padata_free_pd(ps->opd);
+		padata_put_pd(ps->opd);
 
 	pinst->flags &= ~PADATA_RESET;
 
@@ -966,7 +993,7 @@ static ssize_t padata_sysfs_store(struct kobject *kobj, struct attribute *attr,
 
 	pinst = kobj2pinst(kobj);
 	pentry = attr2pentry(attr);
-	if (pentry->show)
+	if (pentry->store)
 		ret = pentry->store(pinst, attr, buf, count);
 
 	return ret;
@@ -1117,11 +1144,16 @@ void padata_free_shell(struct padata_shell *ps)
 	if (!ps)
 		return;
 
+	/*
+	 * Wait for all _do_serial calls to finish to avoid touching
+	 * freed pd's and ps's.
+	 */
+	synchronize_rcu();
+
 	mutex_lock(&ps->pinst->lock);
 	list_del(&ps->list);
 	pd = rcu_dereference_protected(ps->pd, 1);
-	if (refcount_dec_and_test(&pd->refcnt))
-		padata_free_pd(pd);
+	padata_put_pd(pd);
 	mutex_unlock(&ps->pinst->lock);
 
 	kfree(ps);