Commit 00f89d21 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by James Morris
Browse files

mm_for_maps: shift down_read(mmap_sem) to the caller



mm_for_maps() takes ->mmap_sem after security checks, this looks
strange and obfuscates the locking rules. Move this lock to its
single caller, m_start().
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent 13f0feaf
......@@ -235,9 +235,8 @@ static int check_mem_permission(struct task_struct *task)
struct mm_struct *mm_for_maps(struct task_struct *task)
{
struct mm_struct *mm = get_task_mm(task);
if (!mm)
return NULL;
if (mm != current->mm) {
if (mm && mm != current->mm) {
/*
* task->mm can be changed before security check,
* in that case we must notice the change after.
......@@ -245,10 +244,9 @@ struct mm_struct *mm_for_maps(struct task_struct *task)
if (!ptrace_may_access(task, PTRACE_MODE_READ) ||
mm != task->mm) {
mmput(mm);
return NULL;
mm = NULL;
}
}
down_read(&mm->mmap_sem);
return mm;
}
......
......@@ -119,6 +119,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
mm = mm_for_maps(priv->task);
if (!mm)
return NULL;
down_read(&mm->mmap_sem);
tail_vma = get_gate_vma(priv->task);
priv->tail_vma = tail_vma;
......
......@@ -189,6 +189,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
priv->task = NULL;
return NULL;
}
down_read(&mm->mmap_sem);
/* start from the Nth VMA */
for (p = rb_first(&mm->mm_rb); p; p = rb_next(p))
......
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