Messages in this thread Patch in this message | | | Date | Thu, 13 Aug 2009 12:50:42 -0700 | From | Greg KH <> | Subject | [patch 67/74] mm_for_maps: simplify, use ptrace_may_access() |
| |
2.6.30-stable review patch. If anyone has any objections, please let us know.
------------------
From: Oleg Nesterov <oleg@redhat.com>
commit 13f0feafa6b8aead57a2a328e2fca6a5828bf286 upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/proc/base.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-)
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -237,20 +237,19 @@ struct mm_struct *mm_for_maps(struct tas 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)
| |