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Subject[PATCH] fsi: occ: Prevent use after free
Date
Use get_device and put_device in the open and close functions to
make sure the device doesn't get freed while a file descriptor is
open.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
drivers/fsi/fsi-occ.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/fsi/fsi-occ.c b/drivers/fsi/fsi-occ.c
index c9cc75fbdfb9..9e48dc62b1c5 100644
--- a/drivers/fsi/fsi-occ.c
+++ b/drivers/fsi/fsi-occ.c
@@ -82,6 +82,9 @@ static int occ_open(struct inode *inode, struct file *file)
struct miscdevice *mdev = file->private_data;
struct occ *occ = to_occ(mdev);

+ if (!occ->buffer)
+ return -ENOENT;
+
if (!client)
return -ENOMEM;

@@ -94,6 +97,7 @@ static int occ_open(struct inode *inode, struct file *file)
client->occ = occ;
mutex_init(&client->lock);
file->private_data = client;
+ get_device(occ->dev);

/* We allocate a 1-page buffer, make sure it all fits */
BUILD_BUG_ON((OCC_CMD_DATA_BYTES + 3) > PAGE_SIZE);
@@ -143,7 +147,7 @@ static ssize_t occ_write(struct file *file, const char __user *buf,
ssize_t rc;
u8 *cmd;

- if (!client)
+ if (!client || !client->occ->buffer)
return -ENODEV;

if (len > (OCC_CMD_DATA_BYTES + 3) || len < 3)
@@ -197,6 +201,7 @@ static int occ_release(struct inode *inode, struct file *file)
{
struct occ_client *client = file->private_data;

+ put_device(client->occ->dev);
free_page((unsigned long)client->buffer);
kfree(client);

@@ -672,6 +677,7 @@ static int occ_remove(struct platform_device *pdev)
struct occ *occ = platform_get_drvdata(pdev);

kvfree(occ->buffer);
+ occ->buffer = NULL;

misc_deregister(&occ->mdev);

--
2.27.0
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