linux-kernel - [PATCH] NFC: nci: fix memory leak in nci_rx_data

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Date:   Fri, 18 Nov 2022 16:24:19 +0800
From:   Liu Shixin <liushixin2@...wei.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Liu Shixin <liushixin2@...wei.com>
Subject: [PATCH] NFC: nci: fix memory leak in nci_rx_data_packet()

Syzbot reported a memory leak about skb:

unreferenced object 0xffff88810e144e00 (size 240):
  comm "syz-executor284", pid 3701, jiffies 4294952403 (age 12.620s)
  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:
    [<ffffffff83ab79a9>] __alloc_skb+0x1f9/0x270 net/core/skbuff.c:497
    [<ffffffff82a5cf64>] alloc_skb include/linux/skbuff.h:1267 [inline]
    [<ffffffff82a5cf64>] virtual_ncidev_write+0x24/0xe0 drivers/nfc/virtual_ncidev.c:116
    [<ffffffff815f6503>] do_loop_readv_writev fs/read_write.c:759 [inline]
    [<ffffffff815f6503>] do_loop_readv_writev fs/read_write.c:743 [inline]
    [<ffffffff815f6503>] do_iter_write+0x253/0x300 fs/read_write.c:863
    [<ffffffff815f66ed>] vfs_writev+0xdd/0x240 fs/read_write.c:934
    [<ffffffff815f68f6>] do_writev+0xa6/0x1c0 fs/read_write.c:977
    [<ffffffff848802d5>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [<ffffffff848802d5>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    [<ffffffff84a00087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

In nci_rx_data_packet(), if we don't get a valid conn_info, we will return
directly but forget to release the skb.

Reported-by: syzbot+cdb9a427d1bc08815104@...kaller.appspotmail.com
Fixes: 4aeee6871e8c ("NFC: nci: Add dynamic logical connections support")
Signed-off-by: Liu Shixin <liushixin2@...wei.com>
---
 net/nfc/nci/data.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/nfc/nci/data.c b/net/nfc/nci/data.c
index aa5e712adf07..3d36ea5701f0 100644
--- a/net/nfc/nci/data.c
+++ b/net/nfc/nci/data.c
@@ -279,8 +279,10 @@ void nci_rx_data_packet(struct nci_dev *ndev, struct sk_buff *skb)
 		 nci_plen(skb->data));
 
 	conn_info = nci_get_conn_info_by_conn_id(ndev, nci_conn_id(skb->data));
-	if (!conn_info)
+	if (!conn_info) {
+		kfree_skb(skb);
 		return;
+	}
 
 	/* strip the nci data header */
 	skb_pull(skb, NCI_DATA_HDR_SIZE);
-- 
2.25.1