From 7c9524d929648935bac2bbb4c20437df8f9c3f42 Mon Sep 17 00:00:00 2001
From: Hawkins Jiawei <yin31149@gmail.com>
Date: Tue, 18 Oct 2022 10:18:51 +0800
Subject: [PATCH] Bluetooth: L2CAP: Fix memory leak in vhci_write
Git-commit: 7c9524d929648935bac2bbb4c20437df8f9c3f42
Patch-mainline: v6.1-rc4
References: CVE-2022-3619 bsc#1204569

Syzkaller reports a memory leak as follows:
====================================
Bug: memory leak
unreferenced object 0xffff88810d81ac00 (size 240):
  [...]
  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:
    [<ffffffff838733d9>] __alloc_skb+0x1f9/0x270 net/core/skbuff.c:418
    [<ffffffff833f742f>] alloc_skb include/linux/skbuff.h:1257 [inline]
    [<ffffffff833f742f>] bt_skb_alloc include/net/bluetooth/bluetooth.h:469 [inline]
    [<ffffffff833f742f>] vhci_get_user drivers/bluetooth/hci_vhci.c:391 [inline]
    [<ffffffff833f742f>] vhci_write+0x5f/0x230 drivers/bluetooth/hci_vhci.c:511
    [<ffffffff815e398d>] call_write_iter include/linux/fs.h:2192 [inline]
    [<ffffffff815e398d>] new_sync_write fs/read_write.c:491 [inline]
    [<ffffffff815e398d>] vfs_write+0x42d/0x540 fs/read_write.c:578
    [<ffffffff815e3cdd>] ksys_write+0x9d/0x160 fs/read_write.c:631
    [<ffffffff845e0645>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [<ffffffff845e0645>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    [<ffffffff84600087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
====================================

HCI core will uses hci_rx_work() to process frame, which is queued to
the hdev->rx_q tail in hci_recv_frame() by HCI driver.

Yet the problem is that, HCI core may not free the skb after handling
ACL data packets. To be more specific, when start fragment does not
contain the L2CAP length, HCI core just copies skb into conn->rx_skb and
finishes frame process in l2cap_recv_acldata(), without freeing the skb,
which triggers the above memory leak.

This patch solves it by releasing the relative skb, after processing
the above case in l2cap_recv_acldata().

Fixes: 4d7ea8ee90e4 ("Bluetooth: L2CAP: Fix handling fragmented length")
Link: https://lore.kernel.org/all/0000000000000d0b1905e6aaef64@google.com/
Reported-and-tested-by: syzbot+8f819e36e01022991cfa@syzkaller.appspotmail.com
Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/bluetooth/l2cap_core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 9a32ce634919..1fbe087d6ae4 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -8461,9 +8461,8 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 		 * expected length.
 		 */
 		if (skb->len < L2CAP_LEN_SIZE) {
-			if (l2cap_recv_frag(conn, skb, conn->mtu) < 0)
-				goto drop;
-			return;
+			l2cap_recv_frag(conn, skb, conn->mtu);
+			break;
 		}
 
 		len = get_unaligned_le16(skb->data) + L2CAP_HDR_SIZE;
@@ -8507,7 +8506,7 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 
 			/* Header still could not be read just continue */
 			if (conn->rx_skb->len < L2CAP_LEN_SIZE)
-				return;
+				break;
 		}
 
 		if (skb->len > conn->rx_len) {
-- 
2.35.3