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authorOleg Nesterov <oleg@redhat.com>2009-07-10 03:27:38 +0200
committerJames Morris <jmorris@namei.org>2009-08-10 20:48:32 +1000
commit00f89d218523b9bf6b522349c039d5ac80aa536d (patch)
treecde7a8bde2798e4fb3ae28756f6cedd4db9191cc
parent13f0feafa6b8aead57a2a328e2fca6a5828bf286 (diff)
downloadconfigs-00f89d218523b9bf6b522349c039d5ac80aa536d.tar.gz
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: Oleg Nesterov <oleg@redhat.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
-rw-r--r--fs/proc/base.c8
-rw-r--r--fs/proc/task_mmu.c1
-rw-r--r--fs/proc/task_nommu.c1
3 files changed, 5 insertions, 5 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 917f338a673..f3c2e4085fe 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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;
}
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6f61b7cc32e..9bd8be1d235 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -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;
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 64a72e2e765..8f5c05d3dbd 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -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))