From 8cdb878dcb359fd1137e9abdee9322f5e9bcfdf8 Mon Sep 17 00:00:00 2001 From: Christopher Yeoh Date: Thu, 2 Feb 2012 11:34:09 +1030 Subject: Fix race in process_vm_rw_core This fixes the race in process_vm_core found by Oleg (see http://article.gmane.org/gmane.linux.kernel/1235667/ for details). This has been updated since I last sent it as the creation of the new mm_access() function did almost exactly the same thing as parts of the previous version of this patch did. In order to use mm_access() even when /proc isn't enabled, we move it to kernel/fork.c where other related process mm access functions already are. Signed-off-by: Chris Yeoh Signed-off-by: Linus Torvalds --- kernel/fork.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 051f090..1b2ef3c 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -647,6 +647,26 @@ struct mm_struct *get_task_mm(struct task_struct *task) } EXPORT_SYMBOL_GPL(get_task_mm); +struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) +{ + struct mm_struct *mm; + int err; + + err = mutex_lock_killable(&task->signal->cred_guard_mutex); + if (err) + return ERR_PTR(err); + + mm = get_task_mm(task); + if (mm && mm != current->mm && + !ptrace_may_access(task, mode)) { + mmput(mm); + mm = ERR_PTR(-EACCES); + } + mutex_unlock(&task->signal->cred_guard_mutex); + + return mm; +} + /* Please note the differences between mmput and mm_release. * mmput is called whenever we stop holding onto a mm_struct, * error success whatever. -- cgit v1.1