Hi Ingo, On 12/04/2015 at 04:09 PM, Ingo Molnar wrote: > * Xunlei Pang <[email protected]> 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. Regards, Xunlei > > Thanks, > > Ingo > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
