linux-kernel - [PATCH v2] media: dvb-usb: fix memory leak in dvb_usb_adapter

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Message-Id: <20220724214100.593287-1-mazinalhaddad05@gmail.com>
Date:   Mon, 25 Jul 2022 00:41:02 +0300
From:   Mazin Al Haddad <mazinalhaddad05@...il.com>
To:     linux-media@...r.kernel.org
Cc:     mchehab@...nel.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 v2] media: dvb-usb: fix memory leak in dvb_usb_adapter_init()

Fix a memory leak in dvb_usb_adapter_init() reported by syzkaller. The 
problem is due to the error path exiting before incrementing 
num_adapters_initalized, which is used as a reference counter to free 
adapter's private data. There are multiple error paths that 
dvb_usb_adapter_init() can exit from before incrementing the counter, 
which lead to a memory leak as the current iteration is not accounted for.
Fix this by freeing the current iteration's adap->priv in each of the 
error paths.

Syz 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?id=4d54f8bf7b98eecf6cd76ed5aaea883c5d9e502a
Reported-by: syzbot+f66dd31987e6740657be@...kaller.appspotmail.com
Signed-off-by: Mazin Al Haddad <mazinalhaddad05@...il.com>
---

Changes in v2:
- Remove variable that is used to refcount and instead free current
  iteration private data.

 drivers/media/usb/dvb-usb/dvb-usb-init.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
index 61439c8f33ca..69520d7ca25d 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
@@ -80,16 +80,22 @@ static int dvb_usb_adapter_init(struct dvb_usb_device *d, short *adapter_nrs)
 		}
 
 		ret = dvb_usb_adapter_stream_init(adap);
-		if (ret)
+		if (ret) {
+			kfree(adap->priv);
 			return ret;
+		}
 
 		ret = dvb_usb_adapter_dvb_init(adap, adapter_nrs);
-		if (ret)
+		if (ret) {
+			kfree(adap->priv);
 			goto dvb_init_err;
+		}
 
 		ret = dvb_usb_adapter_frontend_init(adap);
-		if (ret)
+		if (ret) {
+			kfree(adap->priv);
 			goto frontend_init_err;
+		}
 
 		/* use exclusive FE lock if there is multiple shared FEs */
 		if (adap->fe_adap[1].fe)
@@ -112,6 +118,7 @@ static int dvb_usb_adapter_init(struct dvb_usb_device *d, short *adapter_nrs)
 
 frontend_init_err:
 	dvb_usb_adapter_dvb_exit(adap);
+	return ret;
 dvb_init_err:
 	dvb_usb_adapter_stream_exit(adap);
 	return ret;
-- 
2.37.1