rlimits: allow setrlimit to non-current tasks (1c1e618d) · Commits · 戴 / test

Add locking to allow setrlimit accept task parameter other than current. Namely, lock tasklist_lock for read and check whether the task structure has sighand non-null. Do all the signal processing under that lock still held. There are some points: 1) security_task_setrlimit is now called with that lock held. This is not new, many security_* functions are called with this lock held already so it doesn't harm (all this security_* stuff does almost the same). 2) task->sighand->siglock (in update_rlimit_cpu) is nested in tasklist_lock. This dependence is already existing. 3) tsk->alloc_lock is nested in tasklist_lock. This is OK too, already existing dependence. Signed-off-by:

Jiri Slaby <jirislaby@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com>

kernel/sys.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -1272,6 +1272,7 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,

		#endif

		/* make sure you are allowed to change @tsk limits before calling this */
		int do_setrlimit(struct task_struct *tsk, unsigned int resource,
		struct rlimit *new_rlim)
		{
		@@ -1285,9 +1286,16 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
		if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open)
		return -EPERM;

		/* protect tsk->signal and tsk->sighand from disappearing */
		read_lock(&tasklist_lock);
		if (!tsk->sighand) {
		retval = -ESRCH;
		goto out;
		}

		retval = security_task_setrlimit(tsk->group_leader, resource, new_rlim);
		if (retval)
		return retval;
		goto out;

		if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
		/*
		@@ -1322,6 +1330,7 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,

		update_rlimit_cpu(tsk, new_rlim->rlim_cur);
		out:
		read_unlock(&tasklist_lock);
		return retval;
		}

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