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Commit 2fb9d268 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Jiri Slaby
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rlimits: make sure ->rlim_max never grows in sys_setrlimit 



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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
parent 5ab46b34

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;

}



/*