On Mon, Sep 6, 2021 at 11:47 AM yanghui <yanghui.def@xxxxxxxxxxxxx> wrote: > > Servers happened below panic: > Kernel version:5.4.56 > BUG: unable to handle page fault for address: 0000000000002c48 > RIP: 0010:__next_zones_zonelist+0x1d/0x40 > [264003.977696] RAX: 0000000000002c40 RBX: 0000000000100dca RCX: 0000000000000014 > [264003.977872] Call Trace: > [264003.977888] __alloc_pages_nodemask+0x277/0x310 > [264003.977908] alloc_page_interleave+0x13/0x70 > [264003.977926] handle_mm_fault+0xf99/0x1390 > [264003.977951] __do_page_fault+0x288/0x500 > [264003.977979] ? schedule+0x39/0xa0 > [264003.977994] do_page_fault+0x30/0x110 > [264003.978010] page_fault+0x3e/0x50 > > The reason of panic is that MAX_NUMNODES is passd in the third parameter > in function __alloc_pages_nodemask(preferred_nid). So if to access > zonelist->zoneref->zone_idx in __next_zones_zonelist the panic will happen. > > In offset_il_node(), first_node() return nid from pol->v.nodes, after > this other threads may changed pol->v.nodes before next_node(). > This race condition will let next_node return MAX_NUMNODES.So put > pol->nodes in a local variable. > > The race condition is between offset_il_node and cpuset_change_task_nodemask: > CPU0: CPU1: > alloc_pages_vma() > interleave_nid(pol,) > offset_il_node(pol,) > first_node(pol->v.nodes) cpuset_change_task_nodemask > //nodes==0xc mpol_rebind_task > mpol_rebind_policy > mpol_rebind_nodemask(pol,nodes) > //nodes==0x3 > next_node(nid, pol->v.nodes)//return MAX_NUMNODES > > Signed-off-by: yanghui <yanghui.def@xxxxxxxxxxxxx> LGTM. Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
