Messages in this thread | | | Date | Fri, 4 Dec 2015 09:30:54 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] sched/core: Clear the root_domain cpumasks in init_rootdomain() |
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* Xunlei Pang <xlpang@redhat.com> wrote:
> Hi Ingo, > > On 12/04/2015 at 04:09 PM, Ingo Molnar wrote: > > * Xunlei Pang <xlpang@redhat.com> wrote: > > > >>> Hm, is the alloc_cpumask_var() done in alloc_sched_domains() safe? > >> Until now, I haven't found any other similar issues, but I will check further. > >> > >>> At least the usage pattern in init_sched_domains() looks unsafe: > >>> > >>> doms_cur = alloc_sched_domains(ndoms_cur); > >>> if (!doms_cur) > >>> doms_cur = &fallback_doms; > >>> cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map); > > So is this pattern in init_sched_domains() correct, for OFFSTACK=y? > > > > It looks wrong to me, as alloc_sched_domains() allocates an uninitialized cpumask > > via alloc_cpumask_var() and returns it: > > > > cpumask_var_t *alloc_sched_domains(unsigned int ndoms) > > { > > int i; > > cpumask_var_t *doms; > > > > doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL); > > if (!doms) > > return NULL; > > for (i = 0; i < ndoms; i++) { > > if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) { > > free_sched_domains(doms, i); > > return NULL; > > } > > } > > return doms; > > } > > > > and then this code: > > > >>> cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map); > > uses it without first clearing it. > > > > So is this another such bug, or am I missing something? > > Yeah, I noticed that as well. But fortunately cpumask_andnot(), > cpumask_and() and the like will clear doms_cur[] indirectly, also > cpu_isolated_map, cpu_active_mask, etc doesn't contain any > garbage bits. I also checked the use of it by cpuset, no extra such > bug found by me so far.
Great, thanks for double checking!
Ingo
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