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    Subject[042/264] target: Fix REPORT TARGET PORT GROUPS handling with small allocation length
    3.1-stable review patch.  If anyone has any objections, please let me know.

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

    From: Nicholas Bellinger <nab@linux-iscsi.org>

    commit 6b20fa9aaf0c2f69ee6f9648e20ab2be0206705e upstream.

    This patch fixes a bug with the handling of REPORT TARGET PORT GROUPS
    containing a smaller allocation length than the payload requires causing
    memory writes beyond the end of the buffer. This patch checks for the
    minimum 4 byte length for the response payload length, and also checks
    upon each loop of T10_ALUA(su_dev)->tg_pt_gps_list to ensure the Target
    port group and Target port descriptor list is able to fit into the
    remaining allocation length.

    If the response payload exceeds the allocation length length, then rd_len
    is still increments to indicate to the initiator that the payload has
    been truncated.

    Reported-by: Roland Dreier <roland@purestorage.com>
    Signed-off-by: Nicholas Bellinger <nab@risingtidesystems.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/target/target_core_alua.c | 20 ++++++++++++++++++++
    1 file changed, 20 insertions(+)

    --- a/drivers/target/target_core_alua.c
    +++ b/drivers/target/target_core_alua.c
    @@ -68,6 +68,15 @@ int core_emulate_report_target_port_grou
    unsigned char *buf;
    u32 rd_len = 0, off = 4; /* Skip over RESERVED area to first
    Target port group descriptor */
    + /*
    + * Need at least 4 bytes of response data or else we can't
    + * even fit the return data length.
    + */
    + if (cmd->data_length < 4) {
    + pr_warn("REPORT TARGET PORT GROUPS allocation length %u"
    + " too small\n", cmd->data_length);
    + return -EINVAL;
    + }

    buf = transport_kmap_first_data_page(cmd);

    @@ -75,6 +84,17 @@ int core_emulate_report_target_port_grou
    list_for_each_entry(tg_pt_gp, &su_dev->t10_alua.tg_pt_gps_list,
    tg_pt_gp_list) {
    /*
    + * Check if the Target port group and Target port descriptor list
    + * based on tg_pt_gp_members count will fit into the response payload.
    + * Otherwise, bump rd_len to let the initiator know we have exceeded
    + * the allocation length and the response is truncated.
    + */
    + if ((off + 8 + (tg_pt_gp->tg_pt_gp_members * 4)) >
    + cmd->data_length) {
    + rd_len += 8 + (tg_pt_gp->tg_pt_gp_members * 4);
    + continue;
    + }
    + /*
    * PREF: Preferred target port bit, determine if this
    * bit should be set for port group.
    */



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