lkml.org 
[lkml]   [2018]   [Aug]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v12 05/12] livepatch: Refuse to unload only livepatches available during a forced transition
    Date
    module_put() is currently never called in klp_complete_transition() when
    klp_force is set. As a result, we might keep the reference count even when
    klp_enable_patch() fails and klp_cancel_transition() is called.

    This might make an assumption that a module might get blocked in some
    strange init state. Fortunately, it is not the case. The reference count
    is ignored when mod->init fails and erroneous modules are always removed.

    Anyway, this might make some confusion. Instead, this patch moves
    the global klp_forced flag into struct klp_patch. As a result,
    we block only modules that might still be in use after a forced
    transition. Newly loaded livepatches might be eventually completely
    removed later.

    It is not a big deal. But the code is at least consistent with
    the reality.

    Signed-off-by: Petr Mladek <pmladek@suse.com>
    ---
    include/linux/livepatch.h | 2 ++
    kernel/livepatch/core.c | 4 +++-
    kernel/livepatch/core.h | 1 +
    kernel/livepatch/transition.c | 10 +++++-----
    4 files changed, 11 insertions(+), 6 deletions(-)

    diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
    index 22e0767d64b0..86b484b39326 100644
    --- a/include/linux/livepatch.h
    +++ b/include/linux/livepatch.h
    @@ -138,6 +138,7 @@ struct klp_object {
    * @list: list node for global list of registered patches
    * @kobj: kobject for sysfs resources
    * @enabled: the patch is enabled (but operation may be incomplete)
    + * @forced: was involved in a forced transition
    * @wait_free: wait until the patch is freed
    * @finish: for waiting till it is safe to remove the patch module
    */
    @@ -150,6 +151,7 @@ struct klp_patch {
    struct list_head list;
    struct kobject kobj;
    bool enabled;
    + bool forced;
    bool wait_free;
    struct completion finish;
    };
    diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
    index 3ca404545150..18af1dc0e199 100644
    --- a/kernel/livepatch/core.c
    +++ b/kernel/livepatch/core.c
    @@ -45,7 +45,8 @@
    */
    DEFINE_MUTEX(klp_mutex);

    -static LIST_HEAD(klp_patches);
    +/* Registered patches */
    +LIST_HEAD(klp_patches);

    static struct kobject *klp_root_kobj;

    @@ -660,6 +661,7 @@ static int klp_init_patch(struct klp_patch *patch)
    mutex_lock(&klp_mutex);

    patch->enabled = false;
    + patch->forced = false;
    INIT_LIST_HEAD(&patch->list);
    init_completion(&patch->finish);

    diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
    index 48a83d4364cf..d0cb5390e247 100644
    --- a/kernel/livepatch/core.h
    +++ b/kernel/livepatch/core.h
    @@ -5,6 +5,7 @@
    #include <linux/livepatch.h>

    extern struct mutex klp_mutex;
    +extern struct list_head klp_patches;

    static inline bool klp_is_object_loaded(struct klp_object *obj)
    {
    diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
    index 982a2e4c6120..30a28634c88c 100644
    --- a/kernel/livepatch/transition.c
    +++ b/kernel/livepatch/transition.c
    @@ -33,8 +33,6 @@ struct klp_patch *klp_transition_patch;

    static int klp_target_state = KLP_UNDEFINED;

    -static bool klp_forced = false;
    -
    /*
    * This work can be performed periodically to finish patching or unpatching any
    * "straggler" tasks which failed to transition in the first attempt.
    @@ -137,10 +135,10 @@ static void klp_complete_transition(void)
    klp_target_state == KLP_PATCHED ? "patching" : "unpatching");

    /*
    - * klp_forced set implies unbounded increase of module's ref count if
    + * patch->forced set implies unbounded increase of module's ref count if
    * the module is disabled/enabled in a loop.
    */
    - if (!klp_forced && klp_target_state == KLP_UNPATCHED)
    + if (!klp_transition_patch->forced && klp_target_state == KLP_UNPATCHED)
    module_put(klp_transition_patch->mod);

    klp_target_state = KLP_UNDEFINED;
    @@ -620,6 +618,7 @@ void klp_send_signals(void)
    */
    void klp_force_transition(void)
    {
    + struct klp_patch *patch;
    struct task_struct *g, *task;
    unsigned int cpu;

    @@ -633,5 +632,6 @@ void klp_force_transition(void)
    for_each_possible_cpu(cpu)
    klp_update_patch_state(idle_task(cpu));

    - klp_forced = true;
    + list_for_each_entry(patch, &klp_patches, list)
    + patch->forced = true;
    }
    --
    2.13.7
    \
     
     \ /
      Last update: 2018-08-28 16:39    [W:4.309 / U:0.068 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site