Patch "media: dvbdev: prevent the risk of out of memory access" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    media: dvbdev: prevent the risk of out of memory access

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     media-dvbdev-prevent-the-risk-of-out-of-memory-acces.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 303c5541811002922bcf547f62b8033f51174c3d
Author: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
Date:   Tue Oct 15 15:23:01 2024 +0200

    media: dvbdev: prevent the risk of out of memory access
    
    [ Upstream commit 972e63e895abbe8aa1ccbdbb4e6362abda7cd457 ]
    
    The dvbdev contains a static variable used to store dvb minors.
    
    The behavior of it depends if CONFIG_DVB_DYNAMIC_MINORS is set
    or not. When not set, dvb_register_device() won't check for
    boundaries, as it will rely that a previous call to
    dvb_register_adapter() would already be enforcing it.
    
    On a similar way, dvb_device_open() uses the assumption
    that the register functions already did the needed checks.
    
    This can be fragile if some device ends using different
    calls. This also generate warnings on static check analysers
    like Coverity.
    
    So, add explicit guards to prevent potential risk of OOM issues.
    
    Fixes: 5dd3f3071070 ("V4L/DVB (9361): Dynamic DVB minor allocation")
    Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
index 5124f412c05dc..49d55c5bf717f 100644
--- a/drivers/media/dvb-core/dvbdev.c
+++ b/drivers/media/dvb-core/dvbdev.c
@@ -96,10 +96,15 @@ static DECLARE_RWSEM(minor_rwsem);
 static int dvb_device_open(struct inode *inode, struct file *file)
 {
 	struct dvb_device *dvbdev;
+	unsigned int minor = iminor(inode);
+
+	if (minor >= MAX_DVB_MINORS)
+		return -ENODEV;
 
 	mutex_lock(&dvbdev_mutex);
 	down_read(&minor_rwsem);
-	dvbdev = dvb_minors[iminor(inode)];
+
+	dvbdev = dvb_minors[minor];
 
 	if (dvbdev && dvbdev->fops) {
 		int err = 0;
@@ -539,7 +544,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
 	for (minor = 0; minor < MAX_DVB_MINORS; minor++)
 		if (dvb_minors[minor] == NULL)
 			break;
-	if (minor == MAX_DVB_MINORS) {
+	if (minor >= MAX_DVB_MINORS) {
 		if (new_node) {
 			list_del (&new_node->list_head);
 			kfree(dvbdevfops);
@@ -554,6 +559,14 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
 	}
 #else
 	minor = nums2minor(adap->num, type, id);
+	if (minor >= MAX_DVB_MINORS) {
+		dvb_media_device_free(dvbdev);
+		list_del(&dvbdev->list_head);
+		kfree(dvbdev);
+		*pdvbdev = NULL;
+		mutex_unlock(&dvbdev_register_lock);
+		return ret;
+	}
 #endif
 	dvbdev->minor = minor;
 	dvb_minors[minor] = dvb_device_get(dvbdev);