netdev - [PATCH] net-sysfs: Fix reference count leak

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Date:   Fri, 15 Nov 2019 14:24:12 +0200
From:   jouni.hogander@...kie.com
To:     netdev@...r.kernel.org
Cc:     Jouni Hogander <jouni.hogander@...kie.com>,
        David Miller <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>
Subject: [PATCH] net-sysfs: Fix reference count leak

From: Jouni Hogander <jouni.hogander@...kie.com>

Netdev_register_kobject is calling device_initialize. In case of error
reference taken by device_initialize is not given up. This is
the rootcause for couple of memory leaks reported by Syzkaller:

BUG: memory leak unreferenced object 0xffff8880675ca008 (size 256):
  comm "netdev_register", pid 281, jiffies 4294696663 (age 6.808s)
  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:
    [<0000000058ca4711>] kmem_cache_alloc_trace+0x167/0x280
    [<000000002340019b>] device_add+0x882/0x1750
    [<000000001d588c3a>] netdev_register_kobject+0x128/0x380
    [<0000000011ef5535>] register_netdevice+0xa1b/0xf00
    [<000000007fcf1c99>] __tun_chr_ioctl+0x20d5/0x3dd0
    [<000000006a5b7b2b>] tun_chr_ioctl+0x2f/0x40
    [<00000000f30f834a>] do_vfs_ioctl+0x1c7/0x1510
    [<00000000fba062ea>] ksys_ioctl+0x99/0xb0
    [<00000000b1c1b8d2>] __x64_sys_ioctl+0x78/0xb0
    [<00000000984cabb9>] do_syscall_64+0x16f/0x580
    [<000000000bde033d>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
    [<00000000e6ca2d9f>] 0xffffffffffffffff

BUG: memory leak
unreferenced object 0xffff8880668ba588 (size 8):
  comm "kobject_set_nam", pid 286, jiffies 4294725297 (age 9.871s)
  hex dump (first 8 bytes):
    6e 72 30 00 cc be df 2b                          nr0....+
  backtrace:
    [<00000000a322332a>] __kmalloc_track_caller+0x16e/0x290
    [<00000000236fd26b>] kstrdup+0x3e/0x70
    [<00000000dd4a2815>] kstrdup_const+0x3e/0x50
    [<0000000049a377fc>] kvasprintf_const+0x10e/0x160
    [<00000000627fc711>] kobject_set_name_vargs+0x5b/0x140
    [<0000000019eeab06>] dev_set_name+0xc0/0xf0
    [<0000000069cb12bc>] netdev_register_kobject+0xc8/0x320
    [<00000000f2e83732>] register_netdevice+0xa1b/0xf00
    [<000000009e1f57cc>] __tun_chr_ioctl+0x20d5/0x3dd0
    [<000000009c560784>] tun_chr_ioctl+0x2f/0x40
    [<000000000d759e02>] do_vfs_ioctl+0x1c7/0x1510
    [<00000000351d7c31>] ksys_ioctl+0x99/0xb0
    [<000000008390040a>] __x64_sys_ioctl+0x78/0xb0
    [<0000000052d196b7>] do_syscall_64+0x16f/0x580
    [<0000000019af9236>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
    [<00000000bc384531>] 0xffffffffffffffff

Reported-by: syzbot+ad8ca40ecd77896d51e2@...kaller.appspotmail.com
Cc: David Miller <davem@...emloft.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>
Signed-off-by: Jouni Hogander <jouni.hogander@...kie.com>
---
 net/core/net-sysfs.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 865ba6ca16eb..72ecad583953 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1626,6 +1626,12 @@ static void netdev_release(struct device *d)
 {
 	struct net_device *dev = to_net_dev(d);
 
+	/* Triggered by an error clean-up (put_device) during
+	 * initialization.
+	 */
+	if (dev->reg_state == NETREG_UNINITIALIZED)
+		return;
+
 	BUG_ON(dev->reg_state != NETREG_RELEASED);
 
 	/* no need to wait for rcu grace period:
@@ -1745,16 +1751,21 @@ int netdev_register_kobject(struct net_device *ndev)
 
 	error = device_add(dev);
 	if (error)
-		return error;
+		goto err_device_add;
 
 	error = register_queue_kobjects(ndev);
-	if (error) {
-		device_del(dev);
-		return error;
-	}
+	if (error)
+		goto err_register_queue_kobjects;
 
 	pm_runtime_set_memalloc_noio(dev, true);
 
+	return error;
+
+err_register_queue_kobjects:
+	device_del(dev);
+err_device_add:
+	put_device(dev);
+
 	return error;
 }
 
-- 
2.17.1