lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 28 Aug 2007 17:48:53 +0400 From: Oleg Nesterov <oleg@...sign.ru> To: Cliff Wickman <cpw@....com>, Paul Jackson <pj@....com>, Paul Menage <menage@...gle.com> Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Gautham R Shenoy <ego@...ibm.com>, Srivatsa Vaddagiri <vatsa@...ibm.com> Subject: cpusets vs cpu-hotplug interaction is broken? (cpu-hotplug experts cc'ed) On 08/25, Oleg Nesterov wrote: > > After the brief look at kernel/cpuset.c, it seems that attach_task() should > guarantee that the task can't use CPUs outside of cpuset->cpus_allowed. > > But this looks racy wrt sched_setaffinity() which does > > cpus_allowed = cpuset_cpus_allowed(p); > // callback_mutex is free > set_cpus_allowed(p); > > What if attach_task()->set_cpus_allowed() happens in between? Actually, I think there is another problem, and cpuset_cpus_allowed() is just broken wrt CONFIG_HOTPLUG_CPU. Suppose that CONFIG_CPUSETS is true, but we don't use cpusets. In that case all tasks in system belong to the top_cpuset (btw, why cpuset_init() sets init_task.cpuset? this was already done by cpuset_init_early()), and we should have the same behaviour as without CONFIG_CPUSETS. By default, all tasks have ->cpus_allowed = CPU_MASK_ALL inherited from kernel_init(). This means that the task can use the new CPU right after cpu_up(). Now let's suppose that some task does sched_setaffinity(0, CPU_MASK_ALL). In that case, cpuset_cpus_allowed() sets ->cpus_allowed = cpu_online_map, and I think this is just wrong. Now that task doesn't see the new CPUs. Of course, we have the similar problem with cpusets other than top_cpuset. In short, unless I missed something, top_cpuset.cpus_allowed should be cpu_possible_map, guarantee_online_cpus() shouldn't mix "allowed" and "online" masks. Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists