Merge: Bluetooth: L2CAP: Fix memory leak in vhci_write

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/1958

Bugzilla: https://bugzilla.redhat.com/2155874

CVE: CVE-2022-3619

commit 7c9524d
Author: Hawkins Jiawei <yin31149@gmail.com>
Date:   Tue Oct 18 10:18:51 2022 +0800

    Bluetooth: L2CAP: Fix memory leak in vhci_write

    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: 4d7ea8e ("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>

Signed-off-by: Wander Lairson Costa <wander@redhat.com>

Approved-by: Julia Denham <jdenham@redhat.com>
Approved-by: Ricardo Robaina <rrobaina@redhat.com>

Signed-off-by: Herton R. Krzesinski <herton@redhat.com>

Author: Herton R. Krzesinski

net/bluetooth/l2cap_core.c

@@ -8443,9 +8443,8 @@ 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;
@@ -8489,7 +8488,7 @@ 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) {