[v3] nbd: Fix memory leak in nbd_add_socket
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Message ID 20200622112001.105047-1-zhengbin13@huawei.com
State New
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Series
  • [v3] nbd: Fix memory leak in nbd_add_socket
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Commit Message

Zheng Bin June 22, 2020, 11:20 a.m. UTC
When adding first socket to nbd, if nsock's allocation failed, the data
structure member "config->socks" was reallocated, but the data structure
member "config->num_connections" was not updated. A memory leak will occur
then because the function "nbd_config_put" will free "config->socks" only
when "config->num_connections" is not zero.

Fixes: 03bf73c315ed ("nbd: prevent memory leak")
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
---

v1->v2: improve change description
v2->v3: fix some code style issues, improve change description, thanks to
        Markus for the review.

 drivers/block/nbd.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

--
2.26.0.106.g9fadedd

Comments

Markus Elfring June 22, 2020, 2:25 p.m. UTC | #1
> When adding first socket to nbd, 

…

Can the term “network block device” matter for this change description?


> … A memory leak will occur
> then because the function "nbd_config_put" will free "config->socks" only
> when "config->num_connections" is not zero.

Will an additional imperative wording be helpful for the commit message?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=625d3449788f85569096780592549d0340e9c0c7#n151

Regards,
Markus


…
> +++ b/drivers/block/nbd.c
> @@ -1033,25 +1033,26 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,> +	if (!nsock) {
> +		err = -ENOMEM;
> +		goto put_socket;
>  	}>  	return 0;
> +

I find that the exception handling can be improved a bit more
by adding another jump target.

+e_nomem:
+	err = -ENOMEM;


> +put_socket:
> +	sockfd_put(sock);
> +	return err;
>  }

Would you like to apply any further fine-tuning?

Regards,
Markus

Patch
diff mbox series

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 43cff01a5a67..ce7e9f223b20 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1033,25 +1033,26 @@  static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 	     test_bit(NBD_RT_BOUND, &config->runtime_flags))) {
 		dev_err(disk_to_dev(nbd->disk),
 			"Device being setup by another task");
-		sockfd_put(sock);
-		return -EBUSY;
+		err = -EBUSY;
+		goto put_socket;
+	}
+
+	nsock = kzalloc(sizeof(*nsock), GFP_KERNEL);
+	if (!nsock) {
+		err = -ENOMEM;
+		goto put_socket;
 	}

 	socks = krealloc(config->socks, (config->num_connections + 1) *
 			 sizeof(struct nbd_sock *), GFP_KERNEL);
 	if (!socks) {
-		sockfd_put(sock);
-		return -ENOMEM;
+		kfree(nsock);
+		err = -ENOMEM;
+		goto put_socket;
 	}

 	config->socks = socks;

-	nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
-	if (!nsock) {
-		sockfd_put(sock);
-		return -ENOMEM;
-	}
-
 	nsock->fallback_index = -1;
 	nsock->dead = false;
 	mutex_init(&nsock->tx_lock);
@@ -1063,6 +1064,10 @@  static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 	atomic_inc(&config->live_connections);

 	return 0;
+
+put_socket:
+	sockfd_put(sock);
+	return err;
 }

 static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)