linux-kernel - [PATCH v3] media: dvb-usb: fix memory leak in dvb_usb_adapter

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Message-Id: <20220824012152.539788-1-mazinalhaddad05@gmail.com>
Date:   Wed, 24 Aug 2022 04:21:52 +0300
From:   Mazin Al Haddad <mazinalhaddad05@...il.com>
To:     mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Mazin Al Haddad <mazinalhaddad05@...il.com>,
        syzbot+f66dd31987e6740657be@...kaller.appspotmail.com
Subject: [PATCH v3] media: dvb-usb: fix memory leak in dvb_usb_adapter_init()

Syzbot reports a memory leak in "dvb_usb_adapter_init()".
The leak is due to not accounting for and freeing current iteration's
adapter->priv in case of an error. Currently if an error occurs, 
it will exit before incrementing "num_adapters_initalized", 
which is used as a reference counter to free all adap->priv 
in "dvb_usb_adapter_exit()". There are multiple error paths that
can exit from before incrementing the counter. Including the
error handling paths for "dvb_usb_adapter_stream_init()", 
"dvb_usb_adapter_dvb_init()" and "dvb_usb_adapter_frontend_init()"
within "dvb_usb_adapter_init()".

This means that in case of an error in any of these functions the 
current iteration is not accounted for and the current iteration's 
adap->priv is not freed.

Fix this by freeing the current iteration's adap->priv in the 
"stream_init_err:" label in the error path. The rest of the 
(accounted for) adap->priv objects are freed in dvb_usb_adapter_exit()
as expected using the num_adapters_initalized variable. 

Syzbot report:

BUG: memory leak
unreferenced object 0xffff8881172f1a00 (size 512):
  comm "kworker/0:2", pid 139, jiffies 4294994873 (age 10.960s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
backtrace:
    [<ffffffff844af012>] dvb_usb_adapter_init drivers/media/usb/dvb-usb/dvb-usb-init.c:75 [inline]
    [<ffffffff844af012>] dvb_usb_init drivers/media/usb/dvb-usb/dvb-usb-init.c:184 [inline]
    [<ffffffff844af012>] dvb_usb_device_init.cold+0x4e5/0x79e drivers/media/usb/dvb-usb/dvb-usb-init.c:308
    [<ffffffff830db21d>] dib0700_probe+0x8d/0x1b0 drivers/media/usb/dvb-usb/dib0700_core.c:883
    [<ffffffff82d3fdc7>] usb_probe_interface+0x177/0x370 drivers/usb/core/driver.c:396
    [<ffffffff8274ab37>] call_driver_probe drivers/base/dd.c:542 [inline]
    [<ffffffff8274ab37>] really_probe.part.0+0xe7/0x310 drivers/base/dd.c:621
    [<ffffffff8274ae6c>] really_probe drivers/base/dd.c:583 [inline]
    [<ffffffff8274ae6c>] __driver_probe_device+0x10c/0x1e0 drivers/base/dd.c:752
    [<ffffffff8274af6a>] driver_probe_device+0x2a/0x120 drivers/base/dd.c:782
    [<ffffffff8274b786>] __device_attach_driver+0xf6/0x140 drivers/base/dd.c:899
    [<ffffffff82747c87>] bus_for_each_drv+0xb7/0x100 drivers/base/bus.c:427
    [<ffffffff8274b352>] __device_attach+0x122/0x260 drivers/base/dd.c:970
    [<ffffffff827498f6>] bus_probe_device+0xc6/0xe0 drivers/base/bus.c:487
    [<ffffffff82745cdb>] device_add+0x5fb/0xdf0 drivers/base/core.c:3405
    [<ffffffff82d3d202>] usb_set_configuration+0x8f2/0xb80 drivers/usb/core/message.c:2170
    [<ffffffff82d4dbfc>] usb_generic_driver_probe+0x8c/0xc0 drivers/usb/core/generic.c:238
    [<ffffffff82d3f49c>] usb_probe_device+0x5c/0x140 drivers/usb/core/driver.c:293
    [<ffffffff8274ab37>] call_driver_probe drivers/base/dd.c:542 [inline]
    [<ffffffff8274ab37>] really_probe.part.0+0xe7/0x310 drivers/base/dd.c:621
    [<ffffffff8274ae6c>] really_probe drivers/base/dd.c:583 [inline]
    [<ffffffff8274ae6c>] __driver_probe_device+0x10c/0x1e0 drivers/base/dd.c:752


Link: https://syzkaller.appspot.com/bug?extid=f66dd31987e6740657be
Reported-and-tested-by: syzbot+f66dd31987e6740657be@...kaller.appspotmail.com
Signed-off-by: Mazin Al Haddad <mazinalhaddad05@...il.com>
---
v2->v3:
	- Follow standard kernel pattern by moving error handling 
	to label instead as suggested by Lukas Bulwhan.
	- Adjust commit description to include syzbot report, 
	The "Reported-and-tested-by" tag and clarify the commit message. 

 drivers/media/usb/dvb-usb/dvb-usb-init.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
index 61439c8f33ca..58eea8ab5477 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
@@ -81,7 +81,7 @@ static int dvb_usb_adapter_init(struct dvb_usb_device *d, short *adapter_nrs)
 
 		ret = dvb_usb_adapter_stream_init(adap);
 		if (ret)
-			return ret;
+			goto stream_init_err;
 
 		ret = dvb_usb_adapter_dvb_init(adap, adapter_nrs);
 		if (ret)
@@ -114,6 +114,8 @@ static int dvb_usb_adapter_init(struct dvb_usb_device *d, short *adapter_nrs)
 	dvb_usb_adapter_dvb_exit(adap);
 dvb_init_err:
 	dvb_usb_adapter_stream_exit(adap);
+stream_init_err:
+	kfree(adap->priv);
 	return ret;
 }
 
-- 
2.37.2