mm_for_maps: simplify, use ptrace_may_access()
It would be nice to kill __ptrace_may_access(). It requires task_lock(), but this lock is only needed to read mm->flags in the middle. Convert mm_for_maps() to use ptrace_may_access(), this also simplifies the code a little bit. Also, we do not need to take ->mmap_sem in advance. In fact I think mm_for_maps() should not play with ->mmap_sem at all, the caller should take this lock. With or without this patch, without ->cred_guard_mutex held we can race with exec() and get the new ->mm but check old creds. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
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@ -237,20 +237,19 @@ struct mm_struct *mm_for_maps(struct task_struct *task)
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struct mm_struct *mm = get_task_mm(task);
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if (!mm)
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return NULL;
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if (mm != current->mm) {
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/*
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* task->mm can be changed before security check,
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* in that case we must notice the change after.
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*/
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if (!ptrace_may_access(task, PTRACE_MODE_READ) ||
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mm != task->mm) {
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mmput(mm);
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return NULL;
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}
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}
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down_read(&mm->mmap_sem);
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task_lock(task);
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if (task->mm != mm)
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goto out;
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if (task->mm != current->mm &&
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__ptrace_may_access(task, PTRACE_MODE_READ) < 0)
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goto out;
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task_unlock(task);
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return mm;
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out:
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task_unlock(task);
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up_read(&mm->mmap_sem);
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mmput(mm);
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return NULL;
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}
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static int proc_pid_cmdline(struct task_struct *task, char * buffer)
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