2.6.30-stable review patch. If anyone has any objections, please let us know. ------------------ From: Oleg Nesterov commit 704b836cbf19e885f8366bccb2e4b0474346c02d upstream. The problem is minor, but without ->cred_guard_mutex held we can race with exec() and get the new ->mm but check old creds. Now we do not need to re-check task->mm after ptrace_may_access(), it can't be changed to the new mm under us. Strictly speaking, this also fixes another very minor problem. Unless security check fails or the task exits mm_for_maps() should never return NULL, the caller should get either old or new ->mm. Signed-off-by: Oleg Nesterov Acked-by: Serge Hallyn Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -234,19 +234,19 @@ static int check_mem_permission(struct t struct mm_struct *mm_for_maps(struct task_struct *task) { - struct mm_struct *mm = get_task_mm(task); + struct mm_struct *mm; - if (mm && 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); - mm = NULL; - } + if (mutex_lock_killable(&task->cred_exec_mutex)) + return NULL; + + mm = get_task_mm(task); + if (mm && mm != current->mm && + !ptrace_may_access(task, PTRACE_MODE_READ)) { + mmput(mm); + mm = NULL; } + mutex_unlock(&task->cred_exec_mutex); + return mm; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/