rlimits: make sure ->rlim_max never grows in sys_setrlimit (2fb9d268) · Commits · 戴 / test

Mostly preparation for Jiri's changes, but probably makes sense anyway. sys_setrlimit() checks new_rlim.rlim_max <= old_rlim->rlim_max, but when it takes task_lock() old_rlim->rlim_max can be already lowered. Move this check under task_lock(). Currently this is not important, we can only race with our sub-thread, this means the application is stupid. But when we change the code to allow the update of !current task's limits, it becomes important to make sure ->rlim_max can be lowered "reliably" even if we race with the application doing sys_setrlimit(). Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Signed-off-by:

Jiri Slaby <jslaby@suse.cz>

kernel/sys.c

+8 −7

Original line number	Diff line number	Diff line
		@@ -1283,10 +1283,6 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, 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)
		return -EPERM;

		@@ -1304,11 +1300,16 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
		new_rlim.rlim_cur = 1;
		}

		old_rlim = current->signal->rlim + resource;
		task_lock(current->group_leader);
		if (new_rlim.rlim_max > old_rlim->rlim_max &&
		!capable(CAP_SYS_RESOURCE))
		retval = -EPERM;
		else
		*old_rlim = new_rlim;
		task_unlock(current->group_leader);

		if (resource != RLIMIT_CPU)
		if (retval \|\| resource != RLIMIT_CPU)
		goto out;

		/*
		@@ -1322,7 +1323,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)

		update_rlimit_cpu(current, new_rlim.rlim_cur);
		out:
		return 0;
		return retval;
		}

		/*

Admin message