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mm_for_maps: simplify, use ptrace_may_access()

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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>
This commit is contained in:
Oleg Nesterov 2009-06-23 21:25:32 +02:00 committed by James Morris
parent f4b9a98868
commit 13f0feafa6
1 changed files with 11 additions and 12 deletions
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23
fs/proc/base.c
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@ -237,20 +237,19 @@ 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) {
/*
* task->mm can be changed before security check,
* in that case we must notice the change after.
*/
if (!ptrace_may_access(task, PTRACE_MODE_READ) ||
mm != task->mm) {
mmput(mm);
return NULL;
}
}
down_read(&mm->mmap_sem);
task_lock(task);
if (task->mm != mm)
goto out;
if (task->mm != current->mm &&
__ptrace_may_access(task, PTRACE_MODE_READ) < 0)
goto out;
task_unlock(task);
return mm;
out:
task_unlock(task);
up_read(&mm->mmap_sem);
mmput(mm);
return NULL;
}
static int proc_pid_cmdline(struct task_struct *task, char * buffer)