Merge remote branch 'limits/writable_limits'

2 files changed, 51 insertions, 31 deletions

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 5c9dc228747b..102c34516e76 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -13,16 +13,16 @@
 /*
  * Called after updating RLIMIT_CPU to set timer expiration if necessary.
  */
-void update_rlimit_cpu(unsigned long rlim_new)
+void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
 {
 	cputime_t cputime = secs_to_cputime(rlim_new);
-	struct signal_struct *const sig = current->signal;
+	struct signal_struct *const sig = task->signal;
 
 	if (cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) ||
 	    cputime_gt(sig->it[CPUCLOCK_PROF].expires, cputime)) {
-		spin_lock_irq(&current->sighand->siglock);
-		set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
-		spin_unlock_irq(&current->sighand->siglock);
+		spin_lock_irq(&task->sighand->siglock);
+		set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
+		spin_unlock_irq(&task->sighand->siglock);
 	}
 }
 
diff --git a/kernel/sys.c b/kernel/sys.c
index ce17760d9c51..fad601080405 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1238,43 +1238,50 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
 
 #endif
 
-SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
+/* 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)
 {
-	struct rlimit new_rlim, *old_rlim;
-	int retval;
+	struct rlimit *old_rlim;
+	int retval = 0;
 
-	if (resource >= RLIM_NLIMITS)
+	if (new_rlim->rlim_cur > new_rlim->rlim_max)
 		return -EINVAL;
-	if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
-		return -EFAULT;
-	if (new_rlim.rlim_cur > new_rlim.rlim_max)
-		return -EINVAL;
-	old_rlim = current->signal->rlim + resource;
-	if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
-	    !capable(CAP_SYS_RESOURCE))
-		return -EPERM;
-	if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
+	if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open)
 		return -EPERM;
 
-	retval = security_task_setrlimit(resource, &new_rlim);
-	if (retval)
-		return retval;
+	/* optimization: 'current' doesn't need locking, e.g. setrlimit */
+	if (tsk != current) {
+		/* protect tsk->signal and tsk->sighand from disappearing */
+		read_lock(&tasklist_lock);
+		if (!tsk->sighand) {
+			retval = -ESRCH;
+			goto out;
+		}
+	}
 
-	if (resource == RLIMIT_CPU && new_rlim.rlim_cur == 0) {
+	if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
 		/*
 		 * The caller is asking for an immediate RLIMIT_CPU
 		 * expiry.  But we use the zero value to mean "it was
 		 * never set".  So let's cheat and make it one second
 		 * instead
 		 */
-		new_rlim.rlim_cur = 1;
+		new_rlim->rlim_cur = 1;
 	}
 
-	task_lock(current->group_leader);
-	*old_rlim = new_rlim;
-	task_unlock(current->group_leader);
-
-	if (resource != RLIMIT_CPU)
+	old_rlim = tsk->signal->rlim + resource;
+	task_lock(tsk->group_leader);
+	if ((new_rlim->rlim_max > old_rlim->rlim_max) &&
+				!capable(CAP_SYS_RESOURCE))
+		retval = -EPERM;
+	if (!retval)
+		retval = security_task_setrlimit(tsk, resource, new_rlim);
+	if (!retval)
+		*old_rlim = *new_rlim;
+	task_unlock(tsk->group_leader);
+
+	if (retval || resource != RLIMIT_CPU)
 		goto out;
 
 	/*
@@ -1283,12 +1290,25 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
 	 * very long-standing error, and fixing it now risks breakage of
 	 * applications, so we live with it
 	 */
-	if (new_rlim.rlim_cur == RLIM_INFINITY)
+	if (new_rlim->rlim_cur == RLIM_INFINITY)
 		goto out;
 
-	update_rlimit_cpu(new_rlim.rlim_cur);
+	update_rlimit_cpu(tsk, new_rlim->rlim_cur);
 out:
-	return 0;
+	if (tsk != current)
+		read_unlock(&tasklist_lock);
+	return retval;
+}
+
+SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
+{
+	struct rlimit new_rlim;
+
+	if (resource >= RLIM_NLIMITS)
+		return -EINVAL;
+	if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
+		return -EFAULT;
+	return do_setrlimit(current, resource, &new_rlim);
 }
 
 /*