tcmu: Fix possible overwrite of t_data_sg's last iov[]

If there has BIDI data, its first iov[] will overwrite the last
iov[] for se_cmd->t_data_sg.

To fix this, we can just increase the iov pointer, but this may
introuduce a new memory leakage bug: If the se_cmd->data_length
and se_cmd->t_bidi_data_sg->length are all not aligned up to the
DATA_BLOCK_SIZE, the actual length needed maybe larger than just
sum of them.

So, this could be avoided by rounding all the data lengthes up
to DATA_BLOCK_SIZE.

Reviewed-by: Mike Christie <mchristi@redhat.com>
Tested-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Reviewed-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
Cc: stable@vger.kernel.org # 3.18+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 6a17c78..e58dfd4 100644 (file)
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -394,6 +394,20 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
        return true;
 }
 
+static inline size_t tcmu_cmd_get_data_length(struct tcmu_cmd *tcmu_cmd)
+{
+       struct se_cmd *se_cmd = tcmu_cmd->se_cmd;
+       size_t data_length = round_up(se_cmd->data_length, DATA_BLOCK_SIZE);
+
+       if (se_cmd->se_cmd_flags & SCF_BIDI) {
+               BUG_ON(!(se_cmd->t_bidi_data_sg && se_cmd->t_bidi_data_nents));
+               data_length += round_up(se_cmd->t_bidi_data_sg->length,
+                               DATA_BLOCK_SIZE);
+       }
+
+       return data_length;
+}
+
 static sense_reason_t
 tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
 {
@@ -407,7 +421,7 @@ tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
        uint32_t cmd_head;
        uint64_t cdb_off;
        bool copy_to_data_area;
-       size_t data_length;
+       size_t data_length = tcmu_cmd_get_data_length(tcmu_cmd);
        DECLARE_BITMAP(old_bitmap, DATA_BLOCK_BITS);
 
        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags))
@@ -433,11 +447,6 @@ tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
 
        mb = udev->mb_addr;
        cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
-       data_length = se_cmd->data_length;
-       if (se_cmd->se_cmd_flags & SCF_BIDI) {
-               BUG_ON(!(se_cmd->t_bidi_data_sg && se_cmd->t_bidi_data_nents));
-               data_length += se_cmd->t_bidi_data_sg->length;
-       }
        if ((command_size > (udev->cmdr_size / 2)) ||
            data_length > udev->data_size) {
                pr_warn("TCMU: Request of size %zu/%zu is too big for %u/%zu "
@@ -511,11 +520,14 @@ tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
        entry->req.iov_dif_cnt = 0;
 
        /* Handle BIDI commands */
-       iov_cnt = 0;
-       alloc_and_scatter_data_area(udev, se_cmd->t_bidi_data_sg,
-               se_cmd->t_bidi_data_nents, &iov, &iov_cnt, false);
-       entry->req.iov_bidi_cnt = iov_cnt;
-
+       if (se_cmd->se_cmd_flags & SCF_BIDI) {
+               iov_cnt = 0;
+               iov++;
+               alloc_and_scatter_data_area(udev, se_cmd->t_bidi_data_sg,
+                               se_cmd->t_bidi_data_nents, &iov, &iov_cnt,
+                               false);
+               entry->req.iov_bidi_cnt = iov_cnt;
+       }
        /* cmd's data_bitmap is what changed in process */
        bitmap_xor(tcmu_cmd->data_bitmap, old_bitmap, udev->data_bitmap,
                        DATA_BLOCK_BITS);