2023-05-05 09:29:30

by Dan Carpenter

Subject: [PATCH] mailbox: mailbox-test: fix a locking issue in mbox_test_message_write()

There was a bug where this code forgot to unlock the tdev->mutex if the
kzalloc() failed. Fix this issue, by moving the allocation outside the
lock.

Fixes: 2d1e952a2b8e ("mailbox: mailbox-test: Fix potential double-free in mbox_test_message_write()")
Signed-off-by: Dan Carpenter <[email protected]>
---
drivers/mailbox/mailbox-test.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
index c4a705c30331..fc6a12a51b40 100644
--- a/drivers/mailbox/mailbox-test.c
+++ b/drivers/mailbox/mailbox-test.c
@@ -98,6 +98,7 @@ static ssize_t mbox_test_message_write(struct file *filp,
size_t count, loff_t *ppos)
{
struct mbox_test_device *tdev = filp->private_data;
+ char *message;
void *data;
int ret;

@@ -113,12 +114,13 @@ static ssize_t mbox_test_message_write(struct file *filp,
return -EINVAL;
}

- mutex_lock(&tdev->mutex);
-
- tdev->message = kzalloc(MBOX_MAX_MSG_LEN, GFP_KERNEL);
- if (!tdev->message)
+ message = kzalloc(MBOX_MAX_MSG_LEN, GFP_KERNEL);
+ if (!message)
return -ENOMEM;

+ mutex_lock(&tdev->mutex);
+
+ tdev->message = message;
ret = copy_from_user(tdev->message, userbuf, count);
if (ret) {
ret = -EFAULT;
--
2.39.2

2023-05-10 13:42:54

by Lee Jones

Subject: Re: [PATCH] mailbox: mailbox-test: fix a locking issue in mbox_test_message_write()

Good catch, thanks Dan.

On Fri, 05 May 2023, Dan Carpenter wrote:

> There was a bug where this code forgot to unlock the tdev->mutex if the
> kzalloc() failed. Fix this issue, by moving the allocation outside the
> lock.
>
> Fixes: 2d1e952a2b8e ("mailbox: mailbox-test: Fix potential double-free in mbox_test_message_write()")
> Signed-off-by: Dan Carpenter <[email protected]>
> ---
> drivers/mailbox/mailbox-test.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)

Reviewed-by: Lee Jones <[email protected]>

> diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
> index c4a705c30331..fc6a12a51b40 100644
> --- a/drivers/mailbox/mailbox-test.c
> +++ b/drivers/mailbox/mailbox-test.c
> @@ -98,6 +98,7 @@ static ssize_t mbox_test_message_write(struct file *filp,
> size_t count, loff_t *ppos)
> {
> struct mbox_test_device *tdev = filp->private_data;
> + char *message;
> void *data;
> int ret;
>
> @@ -113,12 +114,13 @@ static ssize_t mbox_test_message_write(struct file *filp,
> return -EINVAL;
> }
>
> - mutex_lock(&tdev->mutex);
> -
> - tdev->message = kzalloc(MBOX_MAX_MSG_LEN, GFP_KERNEL);
> - if (!tdev->message)
> + message = kzalloc(MBOX_MAX_MSG_LEN, GFP_KERNEL);
> + if (!message)
> return -ENOMEM;
>
> + mutex_lock(&tdev->mutex);
> +
> + tdev->message = message;
> ret = copy_from_user(tdev->message, userbuf, count);
> if (ret) {
> ret = -EFAULT;
> --
> 2.39.2
>

--
Lee Jones [李琼斯]

2023-05-31 09:18:11

by Lee Jones

Subject: Re: [PATCH] mailbox: mailbox-test: fix a locking issue in mbox_test_message_write()

Jassi,

On Fri, 05 May 2023, Dan Carpenter wrote:

> There was a bug where this code forgot to unlock the tdev->mutex if the
> kzalloc() failed. Fix this issue, by moving the allocation outside the
> lock.
>
> Fixes: 2d1e952a2b8e ("mailbox: mailbox-test: Fix potential double-free in mbox_test_message_write()")

When are you planning on sending this to the -rcs?

> Signed-off-by: Dan Carpenter <[email protected]>
> ---
> drivers/mailbox/mailbox-test.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
> index c4a705c30331..fc6a12a51b40 100644
> --- a/drivers/mailbox/mailbox-test.c
> +++ b/drivers/mailbox/mailbox-test.c
> @@ -98,6 +98,7 @@ static ssize_t mbox_test_message_write(struct file *filp,
> size_t count, loff_t *ppos)
> {
> struct mbox_test_device *tdev = filp->private_data;
> + char *message;
> void *data;
> int ret;
>
> @@ -113,12 +114,13 @@ static ssize_t mbox_test_message_write(struct file *filp,
> return -EINVAL;
> }
>
> - mutex_lock(&tdev->mutex);
> -
> - tdev->message = kzalloc(MBOX_MAX_MSG_LEN, GFP_KERNEL);
> - if (!tdev->message)
> + message = kzalloc(MBOX_MAX_MSG_LEN, GFP_KERNEL);
> + if (!message)
> return -ENOMEM;
>
> + mutex_lock(&tdev->mutex);
> +
> + tdev->message = message;
> ret = copy_from_user(tdev->message, userbuf, count);
> if (ret) {
> ret = -EFAULT;
> --
> 2.39.2
>

--
Lee Jones [李琼斯]