Messages in this thread | | | Date | Tue, 9 Aug 2016 18:29:47 +0200 | From | Mateusz Guzik <> | Subject | Re: [PACTH v1] mm, proc: Implement /proc/<pid>/totmaps |
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On Tue, Aug 09, 2016 at 12:05:43PM -0400, robert.foss@collabora.com wrote: > From: Sonny Rao <sonnyrao@chromium.org> > > This is based on earlier work by Thiago Goncales. It implements a new > per process proc file which summarizes the contents of the smaps file > but doesn't display any addresses. It gives more detailed information > than statm like the PSS (proprotional set size). It differs from the > original implementation in that it doesn't use the full blown set of > seq operations, uses a different termination condition, and doesn't > displayed "Locked" as that was broken on the original implemenation. > > This new proc file provides information faster than parsing the potentially > huge smaps file.
I have no idea about usefulness of this.
The patch is definitely buggy with respect to how it implements actual access to mm.
> +static int totmaps_proc_show(struct seq_file *m, void *data) > +{ > + struct proc_maps_private *priv = m->private; > + struct mm_struct *mm; > + struct vm_area_struct *vma; > + struct mem_size_stats *mss_sum = priv->mss; > + > + /* reference to priv->task already taken */ > + /* but need to get the mm here because */ > + /* task could be in the process of exiting */ > + mm = get_task_mm(priv->task); > + if (!mm || IS_ERR(mm)) > + return -EINVAL; > +
That's not how it's done in smaps.
> +static int totmaps_open(struct inode *inode, struct file *file) > +{ > + struct proc_maps_private *priv; > + int ret = -ENOMEM; > + priv = kzalloc(sizeof(*priv), GFP_KERNEL); > + if (priv) { > + priv->mss = kzalloc(sizeof(*priv->mss), GFP_KERNEL); > + if (!priv->mss) > + return -ENOMEM;
Cases below explicitly kfree(priv). I can't remember whether the close routine gets called if this one fails. Either way, something is wrong here.
> + > + /* we need to grab references to the task_struct */ > + /* at open time, because there's a potential information */ > + /* leak where the totmaps file is opened and held open */ > + /* while the underlying pid to task mapping changes */ > + /* underneath it */ > + priv->task = get_pid_task(proc_pid(inode), PIDTYPE_PID);
This performs no permission checks that I would see. If you take a look at smaps you will see the user ends up in proc_maps_open which performs proc_mem_open(inode, PTRACE_MODE_READ) and gets a mm from there.
> + if (!priv->task) { > + kfree(priv->mss); > + kfree(priv); > + return -ESRCH; > + } > + > + ret = single_open(file, totmaps_proc_show, priv); > + if (ret) { > + put_task_struct(priv->task); > + kfree(priv->mss); > + kfree(priv); > + } > + } > + return ret; > +} > +
-- Mateusz Guzik
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