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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Gengming Liu <l.dmxcsnsbh@gmail.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 081/121] atm: fix a memory leak of vcc->user_back
Date:   Tue, 29 Sep 2020 13:00:25 +0200
Message-Id: <20200929105934.197711441@linuxfoundation.org>
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From: Cong Wang <xiyou.wangcong@gmail.com>

[ Upstream commit 8d9f73c0ad2f20e9fed5380de0a3097825859d03 ]

In lec_arp_clear_vccs() only entry->vcc is freed, but vcc
could be installed on entry->recv_vcc too in lec_vcc_added().

This fixes the following memory leak:

unreferenced object 0xffff8880d9266b90 (size 16):
  comm "atm2", pid 425, jiffies 4294907980 (age 23.488s)
  hex dump (first 16 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 6b 6b 6b a5  ............kkk.
  backtrace:
    [<(____ptrval____)>] kmem_cache_alloc_trace+0x10e/0x151
    [<(____ptrval____)>] lane_ioctl+0x4b3/0x569
    [<(____ptrval____)>] do_vcc_ioctl+0x1ea/0x236
    [<(____ptrval____)>] svc_ioctl+0x17d/0x198
    [<(____ptrval____)>] sock_do_ioctl+0x47/0x12f
    [<(____ptrval____)>] sock_ioctl+0x2f9/0x322
    [<(____ptrval____)>] vfs_ioctl+0x1e/0x2b
    [<(____ptrval____)>] ksys_ioctl+0x61/0x80
    [<(____ptrval____)>] __x64_sys_ioctl+0x16/0x19
    [<(____ptrval____)>] do_syscall_64+0x57/0x65
    [<(____ptrval____)>] entry_SYSCALL_64_after_hwframe+0x49/0xb3

Cc: Gengming Liu <l.dmxcsnsbh@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/atm/lec.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/atm/lec.c b/net/atm/lec.c
index 704892d79bf19..756429c95e859 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -1290,6 +1290,12 @@ static void lec_arp_clear_vccs(struct lec_arp_table *entry)
 		entry->vcc = NULL;
 	}
 	if (entry->recv_vcc) {
+		struct atm_vcc *vcc = entry->recv_vcc;
+		struct lec_vcc_priv *vpriv = LEC_VCC_PRIV(vcc);
+
+		kfree(vpriv);
+		vcc->user_back = NULL;
+
 		entry->recv_vcc->push = entry->old_recv_push;
 		vcc_release_async(entry->recv_vcc, -EPIPE);
 		entry->recv_vcc = NULL;
-- 
2.25.1