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    Subject[PATCH 04/11] target: support zero-size allocation lengths in transport_kmap_data_sg
    Date
    In order to support zero-size allocation lengths, do not assert
    that we have a scatterlist until after checking cmd->data_length.

    But once we do this, we can have two cases of transport_kmap_data_sg
    returning NULL: a zero-size allocation length, or an out-of-memory
    condition. Report the latter using sense codes, so that the SCSI
    command that triggered it will fail.

    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    ---
    drivers/target/target_core_transport.c | 13 +++++++++----
    1 files changed, 9 insertions(+), 4 deletions(-)

    diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
    index 2e55aa9..8facb74 100644
    --- a/drivers/target/target_core_transport.c
    +++ b/drivers/target/target_core_transport.c
    @@ -2185,7 +2185,6 @@ void *transport_kmap_data_sg(struct se_cmd *cmd)
    struct page **pages;
    int i;

    - BUG_ON(!sg);
    /*
    * We need to take into account a possible offset here for fabrics like
    * tcm_loop who may be using a contig buffer from the SCSI midlayer for
    @@ -2193,13 +2192,17 @@ void *transport_kmap_data_sg(struct se_cmd *cmd)
    */
    if (!cmd->t_data_nents)
    return NULL;
    - else if (cmd->t_data_nents == 1)
    +
    + BUG_ON(!sg);
    + if (cmd->t_data_nents == 1)
    return kmap(sg_page(sg)) + sg->offset;

    /* >1 page. use vmap */
    pages = kmalloc(sizeof(*pages) * cmd->t_data_nents, GFP_KERNEL);
    - if (!pages)
    + if (!pages) {
    + cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
    return NULL;
    + }

    /* convert sg[] to pages[] */
    for_each_sg(cmd->t_data_sg, sg, cmd->t_data_nents, i) {
    @@ -2208,8 +2211,10 @@ void *transport_kmap_data_sg(struct se_cmd *cmd)

    cmd->t_data_vmap = vmap(pages, cmd->t_data_nents, VM_MAP, PAGE_KERNEL);
    kfree(pages);
    - if (!cmd->t_data_vmap)
    + if (!cmd->t_data_vmap) {
    + cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
    return NULL;
    + }

    return cmd->t_data_vmap + cmd->t_data_sg[0].offset;
    }
    --
    1.7.1



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