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drm/i915: Fix refcount leak and possible NULL pointerdereference.
Since get_pid_task() grabs a reference on the task_struct, we have to drop the refcount after reading that task's comm name. Use pid_task() with RCU instead. Also, avoid directly reading like pid_task()->comm because pid_task() will return NULL if the task have already exit()ed. This patch fixes both problems. Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
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@ -404,16 +404,26 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
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seq_putc(m, '\n');
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list_for_each_entry_reverse(file, &dev->filelist, lhead) {
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struct file_stats stats;
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struct task_struct *task;
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memset(&stats, 0, sizeof(stats));
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idr_for_each(&file->object_idr, per_file_stats, &stats);
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/*
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* Although we have a valid reference on file->pid, that does
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* not guarantee that the task_struct who called get_pid() is
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* still alive (e.g. get_pid(current) => fork() => exit()).
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* Therefore, we need to protect this ->comm access using RCU.
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*/
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rcu_read_lock();
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task = pid_task(file->pid, PIDTYPE_PID);
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seq_printf(m, "%s: %u objects, %zu bytes (%zu active, %zu inactive, %zu unbound)\n",
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get_pid_task(file->pid, PIDTYPE_PID)->comm,
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task ? task->comm : "<unknown>",
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stats.count,
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stats.total,
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stats.active,
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stats.inactive,
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stats.unbound);
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rcu_read_unlock();
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}
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mutex_unlock(&dev->struct_mutex);
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