From: Mike Marciniszyn <mike.marciniszyn@intel.com>
Date: Fri, 12 Aug 2016 15:17:37 +0000 (-0400)
Subject: IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
X-Git-Tag: v4.7.5~129
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1c94558c5df3e05f6d0051f947087441f9ff56d4;p=thirdparty%2Fkernel%2Fstable.git

IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held

commit c62fb260a86dde3df5b2905432caa0e9f6898434 upstream.

The qp init function does a kzalloc() while holding the RCU
lock that encounters the following warning with a debug kernel
when a cat of the qp_stats is done:

[  231.723948] rcu_scheduler_active = 1, debug_locks = 0
[  231.731939] 3 locks held by cat/11355:
[  231.736492]  #0:  (debugfs_srcu){......}, at: [<ffffffff813001a5>] debugfs_use_file_start+0x5/0x90
[  231.746955]  #1:  (&p->lock){+.+.+.}, at: [<ffffffff81289a6c>] seq_read+0x4c/0x3c0
[  231.755873]  #2:  (rcu_read_lock){......}, at: [<ffffffffa0a0c535>] _qp_stats_seq_start+0x5/0xd0 [hfi1]
[  231.766862]

The init functions do an implicit next which requires the rcu read lock
before the kzalloc().

Fix for both drivers is to change the scope of the init function to only
do the allocation and the initialization of the just allocated iter.

The implict next is moved back into the respective start functions to fix
the issue.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
index dbab9d9cc288c..a49cc88f08a2a 100644
--- a/drivers/infiniband/hw/hfi1/debugfs.c
+++ b/drivers/infiniband/hw/hfi1/debugfs.c
@@ -223,28 +223,32 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
 DEBUGFS_FILE_OPS(ctx_stats);
 
 static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
-__acquires(RCU)
+	__acquires(RCU)
 {
 	struct qp_iter *iter;
 	loff_t n = *pos;
 
-	rcu_read_lock();
 	iter = qp_iter_init(s->private);
+
+	/* stop calls rcu_read_unlock */
+	rcu_read_lock();
+
 	if (!iter)
 		return NULL;
 
-	while (n--) {
+	do {
 		if (qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
+	} while (n--);
 
 	return iter;
 }
 
 static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 				loff_t *pos)
+	__must_hold(RCU)
 {
 	struct qp_iter *iter = iter_ptr;
 
@@ -259,7 +263,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
-__releases(RCU)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
diff --git a/drivers/infiniband/hw/hfi1/qp.c b/drivers/infiniband/hw/hfi1/qp.c
index 1a942ffba4cb0..995c897669b2e 100644
--- a/drivers/infiniband/hw/hfi1/qp.c
+++ b/drivers/infiniband/hw/hfi1/qp.c
@@ -595,10 +595,6 @@ struct qp_iter *qp_iter_init(struct hfi1_ibdev *dev)
 
 	iter->dev = dev;
 	iter->specials = dev->rdi.ibdev.phys_port_cnt * 2;
-	if (qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }
diff --git a/drivers/infiniband/hw/qib/qib_debugfs.c b/drivers/infiniband/hw/qib/qib_debugfs.c
index 5e75b43c596b6..5bad8e3b40bb3 100644
--- a/drivers/infiniband/hw/qib/qib_debugfs.c
+++ b/drivers/infiniband/hw/qib/qib_debugfs.c
@@ -189,27 +189,32 @@ static int _ctx_stats_seq_show(struct seq_file *s, void *v)
 DEBUGFS_FILE(ctx_stats)
 
 static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
+	__acquires(RCU)
 {
 	struct qib_qp_iter *iter;
 	loff_t n = *pos;
 
-	rcu_read_lock();
 	iter = qib_qp_iter_init(s->private);
+
+	/* stop calls rcu_read_unlock */
+	rcu_read_lock();
+
 	if (!iter)
 		return NULL;
 
-	while (n--) {
+	do {
 		if (qib_qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
+	} while (n--);
 
 	return iter;
 }
 
 static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 				   loff_t *pos)
+	__must_hold(RCU)
 {
 	struct qib_qp_iter *iter = iter_ptr;
 
@@ -224,6 +229,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c
index 575b737d9ef3d..7119a7da289f3 100644
--- a/drivers/infiniband/hw/qib/qib_qp.c
+++ b/drivers/infiniband/hw/qib/qib_qp.c
@@ -530,10 +530,6 @@ struct qib_qp_iter *qib_qp_iter_init(struct qib_ibdev *dev)
 		return NULL;
 
 	iter->dev = dev;
-	if (qib_qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }