• Nicholas Bellinger's avatar
    target: Fix race for SCF_COMPARE_AND_WRITE_POST checking · 2f3897ea
    Nicholas Bellinger authored
    commit 057085e5 upstream.
    
    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>
    Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    [ luis: backported to 3.16: adjusted context ]
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    2f3897ea
target_core_base.h 26.2 KB