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Message-ID: <20180601125037.GA2339@hle-laptop.local>
Date: Fri, 1 Jun 2018 08:50:37 -0400
From: Hugo Lefeuvre <hle@....eu.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: kernelnewbies@...nelnewbies.org, devel@...verdev.osuosl.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] staging: pi433: add rw semaphore fixing concurrency issues
Add a rw semaphore fixing potential NULL pointer dereferences in the
pi433 driver.
If pi433_release and pi433_ioctl are concurrently called,
pi433_release might set filp->private_data to NULL while pi433_ioctl
is still accessing it, leading to NULL pointer dereference. This issue
might also affect pi433_write and pi433_read.
The newly introduced semaphore makes sure that filp->private_data
will not be freed by pi433_release (writer) as long as pi433_write,
pi433_read or pi433_ioctl (readers) are still executing.
Signed-off-by: Hugo Lefeuvre <hle@....eu.com>
---
drivers/staging/pi433/pi433_if.c | 25 ++++++++++++++++++++++---
1 file changed, 22 insertions(+), 3 deletions(-)
diff --git a/drivers/staging/pi433/pi433_if.c b/drivers/staging/pi433/pi433_if.c
index d1e0ddbc79ce..ce83139cc795 100644
--- a/drivers/staging/pi433/pi433_if.c
+++ b/drivers/staging/pi433/pi433_if.c
@@ -39,6 +39,7 @@
#include <linux/kfifo.h>
#include <linux/errno.h>
#include <linux/mutex.h>
+#include <linux/rwsem.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/interrupt.h>
@@ -116,6 +117,7 @@ struct pi433_device {
struct pi433_instance {
struct pi433_device *device;
struct pi433_tx_cfg tx_cfg;
+ struct rw_semaphore instance_sem;
};
/*-------------------------------------------------------------------------*/
@@ -778,6 +780,7 @@ pi433_read(struct file *filp, char __user *buf, size_t size, loff_t *f_pos)
if (size > MAX_MSG_SIZE)
return -EMSGSIZE;
+ down_read(&instance->instance_sem);
instance = filp->private_data;
device = instance->device;
@@ -785,6 +788,7 @@ pi433_read(struct file *filp, char __user *buf, size_t size, loff_t *f_pos)
mutex_lock(&device->rx_lock);
if (device->rx_active) {
mutex_unlock(&device->rx_lock);
+ up_read(&instance->instance_sem);
return -EAGAIN;
}
@@ -805,9 +809,11 @@ pi433_read(struct file *filp, char __user *buf, size_t size, loff_t *f_pos)
if (bytes_received > 0) {
retval = copy_to_user(buf, device->rx_buffer, bytes_received);
if (retval)
+ up_read(&instance->instance_sem);
return -EFAULT;
}
+ up_read(&instance->instance_sem);
return bytes_received;
}
@@ -820,11 +826,13 @@ pi433_write(struct file *filp, const char __user *buf,
int retval;
unsigned int copied;
+ down_read(&instance->instance_sem);
instance = filp->private_data;
device = instance->device;
/* check, whether internal buffer (tx thread) is big enough for requested size */
if (count > MAX_MSG_SIZE)
+ up_read(&instance->instance_sem);
return -EMSGSIZE;
/* write the following sequence into fifo:
@@ -851,6 +859,7 @@ pi433_write(struct file *filp, const char __user *buf,
/* start transfer */
wake_up_interruptible(&device->tx_wait_queue);
dev_dbg(device->dev, "write: generated new msg with %d bytes.", copied);
+ up_read(&instance->instance_sem);
return copied;
@@ -858,6 +867,7 @@ pi433_write(struct file *filp, const char __user *buf,
dev_dbg(device->dev, "write to fifo failed: 0x%x", retval);
kfifo_reset(&device->tx_fifo); // TODO: maybe find a solution, not to discard already stored, valid entries
mutex_unlock(&device->tx_fifo_lock);
+ up_read(&instance->instance_sem);
return -EAGAIN;
}
@@ -873,29 +883,31 @@ pi433_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
if (_IOC_TYPE(cmd) != PI433_IOC_MAGIC)
return -ENOTTY;
- /* TODO? guard against device removal before, or while,
- * we issue this ioctl. --> device_get()
- */
+ down_read(&instance->instance_sem);
instance = filp->private_data;
device = instance->device;
if (!device)
+ up_read(&instance->instance_sem);
return -ESHUTDOWN;
switch (cmd) {
case PI433_IOC_RD_TX_CFG:
if (copy_to_user(argp, &instance->tx_cfg,
sizeof(struct pi433_tx_cfg)))
+ up_read(&instance->instance_sem);
return -EFAULT;
break;
case PI433_IOC_WR_TX_CFG:
if (copy_from_user(&instance->tx_cfg, argp,
sizeof(struct pi433_tx_cfg)))
+ up_read(&instance->instance_sem);
return -EFAULT;
break;
case PI433_IOC_RD_RX_CFG:
if (copy_to_user(argp, &device->rx_cfg,
sizeof(struct pi433_rx_cfg)))
+ up_read(&instance->instance_sem);
return -EFAULT;
break;
case PI433_IOC_WR_RX_CFG:
@@ -904,21 +916,26 @@ pi433_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
/* during pendig read request, change of config not allowed */
if (device->rx_active) {
mutex_unlock(&device->rx_lock);
+ up_read(&instance->instance_sem);
return -EAGAIN;
}
if (copy_from_user(&device->rx_cfg, argp,
sizeof(struct pi433_rx_cfg))) {
mutex_unlock(&device->rx_lock);
+ up_read(&instance->instance_sem);
return -EFAULT;
}
mutex_unlock(&device->rx_lock);
+ up_read(&instance->instance_sem);
break;
default:
+ up_read(&instance->instance_sem);
retval = -EINVAL;
}
+ up_read(&instance->instance_sem);
return retval;
}
@@ -964,6 +981,7 @@ static int pi433_open(struct inode *inode, struct file *filp)
/* setup instance data*/
instance->device = device;
instance->tx_cfg.bit_rate = 4711;
+ init_rwsem(&instance->instance_sem);
// TODO: fill instance->tx_cfg;
/* instance data as context */
@@ -978,6 +996,7 @@ static int pi433_release(struct inode *inode, struct file *filp)
struct pi433_instance *instance;
struct pi433_device *device;
+ down_write(&instance->instance_sem);
instance = filp->private_data;
device = instance->device;
kfree(instance);
--
2.17.1
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