Messages in this thread | | | Date | Wed, 23 Apr 2014 12:53:41 +0800 | From | Jiang Liu <> | Subject | Re: [Bugfix] sched: fix possible invalid memory access caused by CPU hot-addition |
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On 2014/4/23 9:59, David Rientjes wrote: > On Tue, 22 Apr 2014, Peter Zijlstra wrote: > >> On Tue, Apr 22, 2014 at 01:01:51PM -0700, Andrew Morton wrote: >>> On Tue, 22 Apr 2014 10:15:15 +0200 Peter Zijlstra <peterz@infradead.org> wrote: >>> >>>> On Tue, Apr 22, 2014 at 01:27:15PM +0800, Jiang Liu wrote: >>>>> When calling kzalloc_node(size, flags, node), we should first check >>>>> whether node is onlined, otherwise it may cause invalid memory access >>>>> as below. >>>> >>>> But this is only for memory less node crap, right? >>> >>> um, why are memoryless nodes crap? >> >> Why wouldn't they be? Having CPUs with no local memory seems decidedly >> suboptimal. > > The quick fix for memoryless node issues is usually just do cpu_to_mem() > rather than cpu_to_node() in the caller. This assumes that the arch is > setup correctly to handle memoryless nodes with > CONFIG_HAVE_MEMORYLESS_NODES (and we've had problems recently with > memoryless nodes not being configured correctly on powerpc). > > That type of a fix would probably be better handled in the slab allocator, > though, since kmalloc_node(nid) shouldn't crash just because nid is > memoryless, we should be doing local_memory_node(node) when allocating the > slab pages. > > However, I don't think memoryless nodes are the problem here since Jiang > is testing for !node_online(nid) in his patch, so it's a problem with > cpu_to_node() pointing to an offline node. It makes sense for the page > allocator to crash in such a case, the node id is erroneous. > > So either the cpu-to-node mapping is invalid or alloc_fair_sched_group() > is allocating memory for a cpu on an offline node. The > for_each_possible_cpu() looks suspicious. There's no guarantee that > local_memory_node(node) for an offline node will return anything with > affinity, so falling back to NUMA_NO_NODE looks appropriate in Jiang's > patch. Hi David, That's the case, alloc_fair_sched_group() is trying to allocate memory for CPU in offline node, which then access non-exist NODE_DATA. Thanks! Gerry
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