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    SubjectRe: input0: bad kobj_uevent_env content in show_uevent()
    Date
    Fengguang Wu <fengguang.wu@intel.com> writes:

    > After the __devinit* removal series, I can still get kernel panic in
    > show_uevent(). So there are more sources of bug..
    >
    > Debug patch:
    >
    > @@ -343,8 +343,11 @@ static ssize_t show_uevent(struct device
    > goto out;
    >
    > /* copy keys to file */
    > - for (i = 0; i < env->envp_idx; i++)
    > + dev_err(dev, "uevent %d env[%d]: %s/.../%s\n", env->buflen, env->envp_idx, top_kobj->name, dev->kobj.name);
    > + for (i = 0; i < env->envp_idx; i++) {
    > + printk(KERN_ERR "uevent %d env[%d]: %s\n", (int)count, i, env->envp[i]);
    > count += sprintf(&buf[count], "%s\n", env->envp[i]);
    > + }
    >
    > Oops message, the env[] is again not properly initilized:
    >
    > [ 44.068623] input input0: uevent 61 env[805306368]: input0/.../input0
    > [ 44.069552] uevent 0 env[0]: (null)

    This is a completely different CONFIG_HOTPLUG problem, only
    demonstrating another reason why CONFIG_HOTPLUG should go away. I had a
    hard time trying to disable it anyway ;-)

    The problem this time is lots of code assuming that a call to
    add_uevent_var() will guarantee that env->buflen > 0. This is not true
    if CONFIG_HOTPLUG is unset. So things like this end up overwriting
    env->envp_idx because the array index is -1:

    if (add_uevent_var(env, "MODALIAS="))
    return -ENOMEM;
    len = input_print_modalias(&env->buf[env->buflen - 1],
    sizeof(env->buf) - env->buflen,
    dev, 0);


    Don't know what the best action is, given that there seem to be a *lot*
    of this around the kernel. This patch "fixes" the problem for me, but I
    don't know if it can be considered an appropriate fix:


    diff --git a/include/linux/kobject.h b/include/linux/kobject.h
    index fc615a9..1e57449 100644
    --- a/include/linux/kobject.h
    +++ b/include/linux/kobject.h
    @@ -224,7 +224,7 @@ static inline int kobject_uevent_env(struct kobject *kobj,

    static inline __printf(2, 3)
    int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
    -{ return 0; }
    +{ return -ENOMEM; }

    static inline int kobject_action_type(const char *buf, size_t count,
    enum kobject_action *type)



    Bjørn
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