[PATCH 3/3] drm/msm: Add a way to override processes comm/cmdline

[Rob Clark]

On Thu, Mar 17, 2022 at 1:21 AM Dan Carpenter <dan.carpenter at oracle.com> wrote:
>
> On Wed, Mar 16, 2022 at 05:29:45PM -0700, Rob Clark wrote:
> >       switch (param) {
> > +     case MSM_PARAM_COMM:
> > +     case MSM_PARAM_CMDLINE: {
> > +             char *str, **paramp;
> > +
> > +             str = kmalloc(len + 1, GFP_KERNEL);
>
> if (!str)
>         return -ENOMEM;
>
> > +             if (copy_from_user(str, u64_to_user_ptr(value), len)) {
> > +                     kfree(str);
> > +                     return -EFAULT;
> > +             }
> > +
> > +             /* Ensure string is null terminated: */
> > +             str[len] = '\0';
> > +
> > +             if (param == MSM_PARAM_COMM) {
> > +                     paramp = &ctx->comm;
> > +             } else {
> > +                     paramp = &ctx->cmdline;
> > +             }
> > +
> > +             kfree(*paramp);
> > +             *paramp = str;
> > +
> > +             return 0;
> > +     }
> >       case MSM_PARAM_SYSPROF:
> >               if (!capable(CAP_SYS_ADMIN))
> >                       return -EPERM;
> > diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> > index 4ec62b601adc..68f3f8ade76d 100644
> > --- a/drivers/gpu/drm/msm/msm_gpu.c
> > +++ b/drivers/gpu/drm/msm/msm_gpu.c
> > @@ -364,14 +364,21 @@ static void retire_submits(struct msm_gpu *gpu);
> >
> >  static void get_comm_cmdline(struct msm_gem_submit *submit, char **comm, char **cmd)
> >  {
> > +     struct msm_file_private *ctx = submit->queue->ctx;
> >       struct task_struct *task;
> >
> > +     *comm = kstrdup(ctx->comm, GFP_KERNEL);
> > +     *cmd  = kstrdup(ctx->cmdline, GFP_KERNEL);
> > +
> >       task = get_pid_task(submit->pid, PIDTYPE_PID);
> >       if (!task)
> >               return;
> >
> > -     *comm = kstrdup(task->comm, GFP_KERNEL);
> > -     *cmd = kstrdup_quotable_cmdline(task, GFP_KERNEL);
> > +     if (!*comm)
> > +             *comm = kstrdup(task->comm, GFP_KERNEL);
>
> What?
>
> If the first allocation failed, then this one is going to fail as well.
> Just return -ENOMEM.  Or maybe this is meant to be checking for an empty
> string?

fwiw, if ctx->comm is NULL, the kstrdup() will return NULL, so this
isn't intended to deal with OoM, but the case that comm and/or cmdline
is not overridden.

BR,
-R

>
> > +
> > +     if (!*cmd)
> > +             *cmd = kstrdup_quotable_cmdline(task, GFP_KERNEL);
>
> Same.
>
> >
> >       put_task_struct(task);
> >  }
>
> regards,
> dan carpenter
>