linux-kernel - [PATCH 1/4] memstick: avert possible race condition between idr_pre_get and idr_get

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Date:	Wed, 27 Oct 2010 04:41:08 +1100
From:	"Alex Dubov" <oakad@...oo.com>
To:	"LKML" <linux-kernel@...r.kernel.org>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Maxim Levitsky" <maximlevitsky@...il.com>,
	Alex Dubov <oakad@...oo.com>
Subject: [PATCH 1/4] memstick: avert possible race condition between idr_pre_get and idr_get_new

From: Alex Dubov <oakad@...oo.com>

Signed-off-by: Alex Dubov <oakad@...oo.com>
---
 drivers/memstick/core/memstick.c    |   18 +++++++++++-------
 drivers/memstick/core/mspro_block.c |    6 ++++--
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/memstick/core/memstick.c b/drivers/memstick/core/memstick.c
index c00fe82..17c556c 100644
--- a/drivers/memstick/core/memstick.c
+++ b/drivers/memstick/core/memstick.c
@@ -510,14 +510,18 @@ int memstick_add_host(struct memstick_host *host)
 {
 	int rc;
 
-	if (!idr_pre_get(&memstick_host_idr, GFP_KERNEL))
-		return -ENOMEM;
+	while (1) {
+		if (!idr_pre_get(&memstick_host_idr, GFP_KERNEL))
+			return -ENOMEM;
 
-	spin_lock(&memstick_host_lock);
-	rc = idr_get_new(&memstick_host_idr, host, &host->id);
-	spin_unlock(&memstick_host_lock);
-	if (rc)
-		return rc;
+		spin_lock(&memstick_host_lock);
+		rc = idr_get_new(&memstick_host_idr, host, &host->id);
+		spin_unlock(&memstick_host_lock);
+		if (!rc)
+			break;
+		else if (rc != -EAGAIN)
+			return rc;
+	}
 
 	dev_set_name(&host->dev, "memstick%u", host->id);
 
diff --git a/drivers/memstick/core/mspro_block.c b/drivers/memstick/core/mspro_block.c
index 02362ec..a167938 100644
--- a/drivers/memstick/core/mspro_block.c
+++ b/drivers/memstick/core/mspro_block.c
@@ -1206,10 +1206,12 @@ static int mspro_block_init_disk(struct memstick_dev *card)
 
 	msb->page_size = be16_to_cpu(sys_info->unit_size);
 
-	if (!idr_pre_get(&mspro_block_disk_idr, GFP_KERNEL))
+	mutex_lock(&mspro_block_disk_lock);
+	if (!idr_pre_get(&mspro_block_disk_idr, GFP_KERNEL)) {
+		mutex_unlock(&mspro_block_disk_lock);
 		return -ENOMEM;
+	}
 
-	mutex_lock(&mspro_block_disk_lock);
 	rc = idr_get_new(&mspro_block_disk_idr, card, &disk_id);
 	mutex_unlock(&mspro_block_disk_lock);
 
-- 
1.6.5.1

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