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    Subject[PATCH 5.5 273/399] scsi: iscsi: Dont destroy session if there are outstanding connections
    Date
    From: Nick Black <nlb@google.com>

    [ Upstream commit 54155ed4199c7aa3fd20866648024ab63c96d579 ]

    A faulty userspace that calls destroy_session() before destroying the
    connections can trigger the failure. This patch prevents the issue by
    refusing to destroy the session if there are outstanding connections.

    ------------[ cut here ]------------
    kernel BUG at mm/slub.c:306!
    invalid opcode: 0000 [#1] SMP PTI
    CPU: 1 PID: 1224 Comm: iscsid Not tainted 5.4.0-rc2.iscsi+ #7
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
    RIP: 0010:__slab_free+0x181/0x350
    [...]
    [ 1209.686056] RSP: 0018:ffffa93d4074fae0 EFLAGS: 00010246
    [ 1209.686694] RAX: ffff934efa5ad800 RBX: 000000008010000a RCX: ffff934efa5ad800
    [ 1209.687651] RDX: ffff934efa5ad800 RSI: ffffeb4041e96b00 RDI: ffff934efd402c40
    [ 1209.688582] RBP: ffffa93d4074fb80 R08: 0000000000000001 R09: ffffffffbb5dfa26
    [ 1209.689425] R10: ffff934efa5ad800 R11: 0000000000000001 R12: ffffeb4041e96b00
    [ 1209.690285] R13: ffff934efa5ad800 R14: ffff934efd402c40 R15: 0000000000000000
    [ 1209.691213] FS: 00007f7945dfb540(0000) GS:ffff934efda80000(0000) knlGS:0000000000000000
    [ 1209.692316] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [ 1209.693013] CR2: 000055877fd3da80 CR3: 0000000077384000 CR4: 00000000000006e0
    [ 1209.693897] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    [ 1209.694773] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    [ 1209.695631] Call Trace:
    [ 1209.695957] ? __wake_up_common_lock+0x8a/0xc0
    [ 1209.696712] iscsi_pool_free+0x26/0x40
    [ 1209.697263] iscsi_session_teardown+0x2f/0xf0
    [ 1209.698117] iscsi_sw_tcp_session_destroy+0x45/0x60
    [ 1209.698831] iscsi_if_rx+0xd88/0x14e0
    [ 1209.699370] netlink_unicast+0x16f/0x200
    [ 1209.699932] netlink_sendmsg+0x21a/0x3e0
    [ 1209.700446] sock_sendmsg+0x4f/0x60
    [ 1209.700902] ___sys_sendmsg+0x2ae/0x320
    [ 1209.701451] ? cp_new_stat+0x150/0x180
    [ 1209.701922] __sys_sendmsg+0x59/0xa0
    [ 1209.702357] do_syscall_64+0x52/0x160
    [ 1209.702812] entry_SYSCALL_64_after_hwframe+0x44/0xa9
    [ 1209.703419] RIP: 0033:0x7f7946433914
    [...]
    [ 1209.706084] RSP: 002b:00007fffb99f2378 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
    [ 1209.706994] RAX: ffffffffffffffda RBX: 000055bc869eac20 RCX: 00007f7946433914
    [ 1209.708082] RDX: 0000000000000000 RSI: 00007fffb99f2390 RDI: 0000000000000005
    [ 1209.709120] RBP: 00007fffb99f2390 R08: 000055bc84fe9320 R09: 00007fffb99f1f07
    [ 1209.710110] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000038
    [ 1209.711085] R13: 000055bc8502306e R14: 0000000000000000 R15: 0000000000000000
    Modules linked in:
    ---[ end trace a2d933ede7f730d8 ]---

    Link: https://lore.kernel.org/r/20191226203148.2172200-1-krisman@collabora.com
    Signed-off-by: Nick Black <nlb@google.com>
    Co-developed-by: Salman Qazi <sqazi@google.com>
    Signed-off-by: Salman Qazi <sqazi@google.com>
    Co-developed-by: Junho Ryu <jayr@google.com>
    Signed-off-by: Junho Ryu <jayr@google.com>
    Co-developed-by: Khazhismel Kumykov <khazhy@google.com>
    Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
    Co-developed-by: Gabriel Krisman Bertazi <krisman@collabora.com>
    Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
    Reviewed-by: Lee Duncan <lduncan@suse.com>
    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/scsi/iscsi_tcp.c | 4 ++++
    drivers/scsi/scsi_transport_iscsi.c | 26 +++++++++++++++++++++++---
    2 files changed, 27 insertions(+), 3 deletions(-)

    diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
    index 0bc63a7ab41c8..b5dd1caae5e92 100644
    --- a/drivers/scsi/iscsi_tcp.c
    +++ b/drivers/scsi/iscsi_tcp.c
    @@ -887,6 +887,10 @@ free_host:
    static void iscsi_sw_tcp_session_destroy(struct iscsi_cls_session *cls_session)
    {
    struct Scsi_Host *shost = iscsi_session_to_shost(cls_session);
    + struct iscsi_session *session = cls_session->dd_data;
    +
    + if (WARN_ON_ONCE(session->leadconn))
    + return;

    iscsi_tcp_r2tpool_free(cls_session->dd_data);
    iscsi_session_teardown(cls_session);
    diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
    index ed8d9709b9b96..271afea654e2b 100644
    --- a/drivers/scsi/scsi_transport_iscsi.c
    +++ b/drivers/scsi/scsi_transport_iscsi.c
    @@ -2947,6 +2947,24 @@ iscsi_set_path(struct iscsi_transport *transport, struct iscsi_uevent *ev)
    return err;
    }

    +static int iscsi_session_has_conns(int sid)
    +{
    + struct iscsi_cls_conn *conn;
    + unsigned long flags;
    + int found = 0;
    +
    + spin_lock_irqsave(&connlock, flags);
    + list_for_each_entry(conn, &connlist, conn_list) {
    + if (iscsi_conn_get_sid(conn) == sid) {
    + found = 1;
    + break;
    + }
    + }
    + spin_unlock_irqrestore(&connlock, flags);
    +
    + return found;
    +}
    +
    static int
    iscsi_set_iface_params(struct iscsi_transport *transport,
    struct iscsi_uevent *ev, uint32_t len)
    @@ -3524,10 +3542,12 @@ iscsi_if_recv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, uint32_t *group)
    break;
    case ISCSI_UEVENT_DESTROY_SESSION:
    session = iscsi_session_lookup(ev->u.d_session.sid);
    - if (session)
    - transport->destroy_session(session);
    - else
    + if (!session)
    err = -EINVAL;
    + else if (iscsi_session_has_conns(ev->u.d_session.sid))
    + err = -EBUSY;
    + else
    + transport->destroy_session(session);
    break;
    case ISCSI_UEVENT_UNBIND_SESSION:
    session = iscsi_session_lookup(ev->u.d_session.sid);
    --
    2.20.1


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