Patch "media: vidtv: Fix use-after-free in vidtv_bridge_dvb_init()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    media: vidtv: Fix use-after-free in vidtv_bridge_dvb_init()

to the 5.15-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-vidtv-fix-use-after-free-in-vidtv_bridge_dvb_i.patch
and it can be found in the queue-5.15 subdirectory.

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



commit 5b9acb67ec3546d9595de7067c2ce38e957009f8
Author: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
Date:   Tue Nov 8 15:06:30 2022 +0800

    media: vidtv: Fix use-after-free in vidtv_bridge_dvb_init()
    
    [ Upstream commit ba8d9405935097e296bcf7a942c3a01df0edb865 ]
    
    KASAN reports a use-after-free:
    BUG: KASAN: use-after-free in dvb_dmxdev_release+0x4d5/0x5d0 [dvb_core]
    Call Trace:
     ...
     dvb_dmxdev_release+0x4d5/0x5d0 [dvb_core]
     vidtv_bridge_probe+0x7bf/0xa40 [dvb_vidtv_bridge]
     platform_probe+0xb6/0x170
     ...
    Allocated by task 1238:
     ...
     dvb_register_device+0x1a7/0xa70 [dvb_core]
     dvb_dmxdev_init+0x2af/0x4a0 [dvb_core]
     vidtv_bridge_probe+0x766/0xa40 [dvb_vidtv_bridge]
     ...
    Freed by task 1238:
     dvb_register_device+0x6d2/0xa70 [dvb_core]
     dvb_dmxdev_init+0x2af/0x4a0 [dvb_core]
     vidtv_bridge_probe+0x766/0xa40 [dvb_vidtv_bridge]
     ...
    
    It is because the error handling in vidtv_bridge_dvb_init() is wrong.
    
    First, vidtv_bridge_dmx(dev)_init() will clean themselves when fail, but
    goto fail_dmx(_dev): calls release functions again, which causes
    use-after-free.
    
    Also, in fail_fe, fail_tuner_probe and fail_demod_probe, j = i will cause
    out-of-bound when i finished its loop (i == NUM_FE). And the loop
    releasing is wrong, although now NUM_FE is 1 so it won't cause problem.
    
    Fix this by correctly releasing everything.
    
    Fixes: f90cf6079bf6 ("media: vidtv: add a bridge driver")
    Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
    Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.c b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
index 82620613d56b..dff7265a42ca 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_bridge.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
@@ -459,26 +459,20 @@ static int vidtv_bridge_dvb_init(struct vidtv_dvb *dvb)
 	for (j = j - 1; j >= 0; --j)
 		dvb->demux.dmx.remove_frontend(&dvb->demux.dmx,
 					       &dvb->dmx_fe[j]);
-fail_dmx_dev:
 	dvb_dmxdev_release(&dvb->dmx_dev);
-fail_dmx:
+fail_dmx_dev:
 	dvb_dmx_release(&dvb->demux);
+fail_dmx:
+fail_demod_probe:
+	for (i = i - 1; i >= 0; --i) {
+		dvb_unregister_frontend(dvb->fe[i]);
 fail_fe:
-	for (j = i; j >= 0; --j)
-		dvb_unregister_frontend(dvb->fe[j]);
+		dvb_module_release(dvb->i2c_client_tuner[i]);
 fail_tuner_probe:
-	for (j = i; j >= 0; --j)
-		if (dvb->i2c_client_tuner[j])
-			dvb_module_release(dvb->i2c_client_tuner[j]);
-
-fail_demod_probe:
-	for (j = i; j >= 0; --j)
-		if (dvb->i2c_client_demod[j])
-			dvb_module_release(dvb->i2c_client_demod[j]);
-
+		dvb_module_release(dvb->i2c_client_demod[i]);
+	}
 fail_adapter:
 	dvb_unregister_adapter(&dvb->adapter);
-
 fail_i2c:
 	i2c_del_adapter(&dvb->i2c_adapter);