V4L/DVB (8131): dmx_write: memcpy from user-supplied pointer

... copy to kernel memory first

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

2 files changed, 15 insertions, 4 deletions

diff --git a/drivers/media/dvb/dvb-core/demux.h b/drivers/media/dvb/dvb-core/demux.h
index b0d347daae47..eb91fd808c16 100644
--- a/drivers/media/dvb/dvb-core/demux.h
+++ b/drivers/media/dvb/dvb-core/demux.h
@@ -247,7 +247,7 @@ struct dmx_demux {
         void* priv;                  /* Pointer to private data of the API client */
         int (*open) (struct dmx_demux* demux);
         int (*close) (struct dmx_demux* demux);
-        int (*write) (struct dmx_demux* demux, const char* buf, size_t count);
+        int (*write) (struct dmx_demux* demux, const char __user *buf, size_t count);
         int (*allocate_ts_feed) (struct dmx_demux* demux,
                                  struct dmx_ts_feed** feed,
                                  dmx_ts_cb callback);
diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c b/drivers/media/dvb/dvb-core/dvb_demux.c
index 934e15fffc56..e2eca0b1fe7c 100644
--- a/drivers/media/dvb/dvb-core/dvb_demux.c
+++ b/drivers/media/dvb/dvb-core/dvb_demux.c
@@ -1056,16 +1056,27 @@ static int dvbdmx_close(struct dmx_demux *demux)
         return 0;
 }
 
-static int dvbdmx_write(struct dmx_demux *demux, const char *buf, size_t count)
+static int dvbdmx_write(struct dmx_demux *demux, const char __user *buf, size_t count)
 {
         struct dvb_demux *dvbdemux = (struct dvb_demux *)demux;
+        void *p;
 
         if ((!demux->frontend) || (demux->frontend->source != DMX_MEMORY_FE))
                 return -EINVAL;
 
-        if (mutex_lock_interruptible(&dvbdemux->mutex))
+        p = kmalloc(count, GFP_USER);
+        if (!p)
+                return -ENOMEM;
+        if (copy_from_user(p, buf, count)) {
+                kfree(p);
+                return -EFAULT;
+        }
+        if (mutex_lock_interruptible(&dvbdemux->mutex)) {
+                kfree(p);
                 return -ERESTARTSYS;
-        dvb_dmx_swfilter(dvbdemux, (u8 *)buf, count);
+        }
+        dvb_dmx_swfilter(dvbdemux, p, count);
+        kfree(p);
         mutex_unlock(&dvbdemux->mutex);
 
         if (signal_pending(current))