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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

fs/proc/base.c

+3 −5
Original line number Diff line number Diff line
@@ -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;

}

fs/proc/task_mmu.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

fs/proc/task_nommu.c

+1 −0
Original line number Diff line number Diff line
@@ -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))