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fbdev: smscufx: Fix several use-after-free bugs 

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@gmail.com>
Link: https://lore.kernel.org/linux-fbdev/20221011153436.GA4446@ubuntu/
Cc: <stable@vger.kernel.org>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Hyunwoo Kim 2022-10-20 18:15:44 -07:00 committed by Helge Deller
parent 70281592bf
commit cc67482c9e
1 changed files with 31 additions and 26 deletions
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57
drivers/video/fbdev/smscufx.c
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@ -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);
pr_debug("freeing ufx_data %p", dev);
kfree(dev);
}
static void ufx_ops_destory(struct fb_info *info)
{
struct ufx_data *dev = info->par;
int node = info->node;
/* 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 @@ e_nomem:
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);
}