• Nicholas Bellinger's avatar
    target: Fix race for SCF_COMPARE_AND_WRITE_POST checking · 057085e5
    Nicholas Bellinger authored
    This patch addresses a race + use after free where the first
    stage of COMPARE_AND_WRITE in compare_and_write_callback()
    is rescheduled after the backend sends the secondary WRITE,
    resulting in second stage compare_and_write_post() callback
    completing in target_complete_ok_work() before the first
    can return.
    Because current code depends on checking se_cmd->se_cmd_flags
    after return from se_cmd->transport_complete_callback(),
    this results in first stage having SCF_COMPARE_AND_WRITE_POST
    set, which incorrectly falls through into second stage CAW
    processing code, eventually triggering a NULL pointer
    dereference due to use after free.
    To address this bug, pass in a new *post_ret parameter into
    se_cmd->transport_complete_callback(), and depend upon this
    value instead of ->se_cmd_flags to determine when to return
    or fall through into ->queue_status() code for CAW.
    Cc: Sagi Grimberg <sagig@mellanox.com>
    Cc: <stable@vger.kernel.org> # v3.12+
    Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
target_core_base.h 26.7 KB