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    Subject[PATCH 4.9 06/71] scsi: iscsi: target: Dont use stack buffer for scatterlist
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Laura Abbott <labbott@redhat.com>

    [ Upstream commit 679fcae46c8b2352bba3485d521da070cfbe68e6 ]

    Fedora got a bug report of a crash with iSCSI:

    kernel BUG at include/linux/scatterlist.h:143!
    ...
    RIP: 0010:iscsit_do_crypto_hash_buf+0x154/0x180 [iscsi_target_mod]
    ...
    Call Trace:
    ? iscsi_target_tx_thread+0x200/0x200 [iscsi_target_mod]
    iscsit_get_rx_pdu+0x4cd/0xa90 [iscsi_target_mod]
    ? native_sched_clock+0x3e/0xa0
    ? iscsi_target_tx_thread+0x200/0x200 [iscsi_target_mod]
    iscsi_target_rx_thread+0x81/0xf0 [iscsi_target_mod]
    kthread+0x120/0x140
    ? kthread_create_worker_on_cpu+0x70/0x70
    ret_from_fork+0x3a/0x50

    This is a BUG_ON for using a stack buffer with a scatterlist. There
    are two cases that trigger this bug. Switch to using a dynamically
    allocated buffer for one case and do not assign a NULL buffer in
    another case.

    Signed-off-by: Laura Abbott <labbott@redhat.com>
    Reviewed-by: Mike Christie <mchristi@redhat.com>
    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/target/iscsi/iscsi_target.c | 22 ++++++++++++++--------
    1 file changed, 14 insertions(+), 8 deletions(-)

    --- a/drivers/target/iscsi/iscsi_target.c
    +++ b/drivers/target/iscsi/iscsi_target.c
    @@ -1435,7 +1435,8 @@ static void iscsit_do_crypto_hash_buf(

    sg_init_table(sg, ARRAY_SIZE(sg));
    sg_set_buf(sg, buf, payload_length);
    - sg_set_buf(sg + 1, pad_bytes, padding);
    + if (padding)
    + sg_set_buf(sg + 1, pad_bytes, padding);

    ahash_request_set_crypt(hash, sg, data_crc, payload_length + padding);

    @@ -3949,10 +3950,14 @@ static bool iscsi_target_check_conn_stat
    static void iscsit_get_rx_pdu(struct iscsi_conn *conn)
    {
    int ret;
    - u8 buffer[ISCSI_HDR_LEN], opcode;
    + u8 *buffer, opcode;
    u32 checksum = 0, digest = 0;
    struct kvec iov;

    + buffer = kcalloc(ISCSI_HDR_LEN, sizeof(*buffer), GFP_KERNEL);
    + if (!buffer)
    + return;
    +
    while (!kthread_should_stop()) {
    /*
    * Ensure that both TX and RX per connection kthreads
    @@ -3960,7 +3965,6 @@ static void iscsit_get_rx_pdu(struct isc
    */
    iscsit_thread_check_cpumask(conn, current, 0);

    - memset(buffer, 0, ISCSI_HDR_LEN);
    memset(&iov, 0, sizeof(struct kvec));

    iov.iov_base = buffer;
    @@ -3969,7 +3973,7 @@ static void iscsit_get_rx_pdu(struct isc
    ret = rx_data(conn, &iov, 1, ISCSI_HDR_LEN);
    if (ret != ISCSI_HDR_LEN) {
    iscsit_rx_thread_wait_for_tcp(conn);
    - return;
    + break;
    }

    if (conn->conn_ops->HeaderDigest) {
    @@ -3979,7 +3983,7 @@ static void iscsit_get_rx_pdu(struct isc
    ret = rx_data(conn, &iov, 1, ISCSI_CRC_LEN);
    if (ret != ISCSI_CRC_LEN) {
    iscsit_rx_thread_wait_for_tcp(conn);
    - return;
    + break;
    }

    iscsit_do_crypto_hash_buf(conn->conn_rx_hash,
    @@ -4003,7 +4007,7 @@ static void iscsit_get_rx_pdu(struct isc
    }

    if (conn->conn_state == TARG_CONN_STATE_IN_LOGOUT)
    - return;
    + break;

    opcode = buffer[0] & ISCSI_OPCODE_MASK;

    @@ -4014,13 +4018,15 @@ static void iscsit_get_rx_pdu(struct isc
    " while in Discovery Session, rejecting.\n", opcode);
    iscsit_add_reject(conn, ISCSI_REASON_PROTOCOL_ERROR,
    buffer);
    - return;
    + break;
    }

    ret = iscsi_target_rx_opcode(conn, buffer);
    if (ret < 0)
    - return;
    + break;
    }
    +
    + kfree(buffer);
    }

    int iscsi_target_rx_thread(void *arg)

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