On 10/21/22 03:15, Hyunwoo Kim wrote:
Several types of UAFs can occur when physically removing a USB device.
Adds ufx_ops_destroy() function to .fb_destroy of fb_ops, and
in this function, there is kref_put() that finally calls ufx_free().
This fix prevents multiple UAFs.
Signed-off-by: Hyunwoo Kim <imv4bel@xxxxxxxxx>
Link: https://lore.kernel.org/linux-fbdev/20221011153436.GA4446@ubuntu/
applied.
Thanks!
Helge
---
v2:
The v1 patch fixed several UAFs, but "info" was not kfree()d after the device
was removed by calling the framebuffer_release() function from
ufx_free_framebuffer().
This is because fb_info->count was not 0 at the time the
framebuffer_release() function was called.
Moved the framebuffer_release() function to the ufx_ops_destory() function.
The ufx_ops_destory() function is a .fb_destory ops that is called
after fb_info->count goes to zero.
---
drivers/video/fbdev/smscufx.c | 55 +++++++++++++++++++----------------
1 file changed, 30 insertions(+), 25 deletions(-)
diff --git a/drivers/video/fbdev/smscufx.c b/drivers/video/fbdev/smscufx.c
index e65bdc499c23..9343b7a4ac89 100644
--- a/drivers/video/fbdev/smscufx.c
+++ b/drivers/video/fbdev/smscufx.c
@@ -97,7 +97,6 @@ struct ufx_data {
struct kref kref;
int fb_count;
bool virtualized; /* true when physical usb device not present */
- struct delayed_work free_framebuffer_work;
atomic_t usb_active; /* 0 = update virtual buffer, but no usb traffic */
atomic_t lost_pixels; /* 1 = a render op failed. Need screen refresh */
u8 *edid; /* null until we read edid from hw or get from sysfs */
@@ -1117,15 +1116,24 @@ static void ufx_free(struct kref *kref)
{
struct ufx_data *dev = container_of(kref, struct ufx_data, kref);
- /* this function will wait for all in-flight urbs to complete */
- if (dev->urbs.count > 0)
- ufx_free_urb_list(dev);
+ kfree(dev);
+}
- pr_debug("freeing ufx_data %p", dev);
+static void ufx_ops_destory(struct fb_info *info)
+{
+ struct ufx_data *dev = info->par;
+ int node = info->node;
- kfree(dev);
+ /* Assume info structure is freed after this point */
+ framebuffer_release(info);
+
+ pr_debug("fb_info for /dev/fb%d has been freed", node);
+
+ /* release reference taken by kref_init in probe() */
+ kref_put(&dev->kref, ufx_free);
}
+
static void ufx_release_urb_work(struct work_struct *work)
{
struct urb_node *unode = container_of(work, struct urb_node,
@@ -1134,14 +1142,9 @@ static void ufx_release_urb_work(struct work_struct *work)
up(&unode->dev->urbs.limit_sem);
}
-static void ufx_free_framebuffer_work(struct work_struct *work)
+static void ufx_free_framebuffer(struct ufx_data *dev)
{
- struct ufx_data *dev = container_of(work, struct ufx_data,
- free_framebuffer_work.work);
struct fb_info *info = dev->info;
- int node = info->node;
-
- unregister_framebuffer(info);
if (info->cmap.len != 0)
fb_dealloc_cmap(&info->cmap);
@@ -1153,11 +1156,6 @@ static void ufx_free_framebuffer_work(struct work_struct *work)
dev->info = NULL;
- /* Assume info structure is freed after this point */
- framebuffer_release(info);
-
- pr_debug("fb_info for /dev/fb%d has been freed", node);
-
/* ref taken in probe() as part of registering framebfufer */
kref_put(&dev->kref, ufx_free);
}
@@ -1169,11 +1167,13 @@ static int ufx_ops_release(struct fb_info *info, int user)
{
struct ufx_data *dev = info->par;
+ mutex_lock(&disconnect_mutex);
+
dev->fb_count--;
/* We can't free fb_info here - fbmem will touch it when we return */
if (dev->virtualized && (dev->fb_count == 0))
- schedule_delayed_work(&dev->free_framebuffer_work, HZ);
+ ufx_free_framebuffer(dev);
if ((dev->fb_count == 0) && (info->fbdefio)) {
fb_deferred_io_cleanup(info);
@@ -1186,6 +1186,8 @@ static int ufx_ops_release(struct fb_info *info, int user)
kref_put(&dev->kref, ufx_free);
+ mutex_unlock(&disconnect_mutex);
+
return 0;
}
@@ -1292,6 +1294,7 @@ static const struct fb_ops ufx_ops = {
.fb_blank = ufx_ops_blank,
.fb_check_var = ufx_ops_check_var,
.fb_set_par = ufx_ops_set_par,
+ .fb_destroy = ufx_ops_destory,
};
/* Assumes &info->lock held by caller
@@ -1673,9 +1676,6 @@ static int ufx_usb_probe(struct usb_interface *interface,
goto destroy_modedb;
}
- INIT_DELAYED_WORK(&dev->free_framebuffer_work,
- ufx_free_framebuffer_work);
-
retval = ufx_reg_read(dev, 0x3000, &id_rev);
check_warn_goto_error(retval, "error %d reading 0x3000 register from device", retval);
dev_dbg(dev->gdev, "ID_REV register value 0x%08x", id_rev);
@@ -1748,10 +1748,12 @@ static int ufx_usb_probe(struct usb_interface *interface,
static void ufx_usb_disconnect(struct usb_interface *interface)
{
struct ufx_data *dev;
+ struct fb_info *info;
mutex_lock(&disconnect_mutex);
dev = usb_get_intfdata(interface);
+ info = dev->info;
pr_debug("USB disconnect starting\n");
@@ -1765,12 +1767,15 @@ static void ufx_usb_disconnect(struct usb_interface *interface)
/* if clients still have us open, will be freed on last close */
if (dev->fb_count == 0)
- schedule_delayed_work(&dev->free_framebuffer_work, 0);
+ ufx_free_framebuffer(dev);
- /* release reference taken by kref_init in probe() */
- kref_put(&dev->kref, ufx_free);
+ /* this function will wait for all in-flight urbs to complete */
+ if (dev->urbs.count > 0)
+ ufx_free_urb_list(dev);
- /* consider ufx_data freed */
+ pr_debug("freeing ufx_data %p", dev);
+
+ unregister_framebuffer(info);
mutex_unlock(&disconnect_mutex);
}
