3.2.44-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Samu Kallio <samu.kallio@xxxxxxxxxxxxxxxxx> commit 1160c2779b826c6f5c08e5cc542de58fd1f667d5 upstream. In paravirtualized x86_64 kernels, vmalloc_fault may cause an oops when lazy MMU updates are enabled, because set_pgd effects are being deferred. One instance of this problem is during process mm cleanup with memory cgroups enabled. The chain of events is as follows: - zap_pte_range enables lazy MMU updates - zap_pte_range eventually calls mem_cgroup_charge_statistics, which accesses the vmalloc'd mem_cgroup per-cpu stat area - vmalloc_fault is triggered which tries to sync the corresponding PGD entry with set_pgd, but the update is deferred - vmalloc_fault oopses due to a mismatch in the PUD entries The OOPs usually looks as so: ------------[ cut here ]------------ kernel BUG at arch/x86/mm/fault.c:396! invalid opcode: 0000 [#1] SMP .. snip .. CPU 1 Pid: 10866, comm: httpd Not tainted 3.6.10-4.fc18.x86_64 #1 RIP: e030:[<ffffffff816271bf>] [<ffffffff816271bf>] vmalloc_fault+0x11f/0x208 .. snip .. Call Trace: [<ffffffff81627759>] do_page_fault+0x399/0x4b0 [<ffffffff81004f4c>] ? xen_mc_extend_args+0xec/0x110 [<ffffffff81624065>] page_fault+0x25/0x30 [<ffffffff81184d03>] ? mem_cgroup_charge_statistics.isra.13+0x13/0x50 [<ffffffff81186f78>] __mem_cgroup_uncharge_common+0xd8/0x350 [<ffffffff8118aac7>] mem_cgroup_uncharge_page+0x57/0x60 [<ffffffff8115fbc0>] page_remove_rmap+0xe0/0x150 [<ffffffff8115311a>] ? vm_normal_page+0x1a/0x80 [<ffffffff81153e61>] unmap_single_vma+0x531/0x870 [<ffffffff81154962>] unmap_vmas+0x52/0xa0 [<ffffffff81007442>] ? pte_mfn_to_pfn+0x72/0x100 [<ffffffff8115c8f8>] exit_mmap+0x98/0x170 [<ffffffff810050d9>] ? __raw_callee_save_xen_pmd_val+0x11/0x1e [<ffffffff81059ce3>] mmput+0x83/0xf0 [<ffffffff810624c4>] exit_mm+0x104/0x130 [<ffffffff8106264a>] do_exit+0x15a/0x8c0 [<ffffffff810630ff>] do_group_exit+0x3f/0xa0 [<ffffffff81063177>] sys_exit_group+0x17/0x20 [<ffffffff8162bae9>] system_call_fastpath+0x16/0x1b Calling arch_flush_lazy_mmu_mode immediately after set_pgd makes the changes visible to the consistency checks. RedHat-Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=914737 Tested-by: Josh Boyer <jwboyer@xxxxxxxxxx> Reported-and-Tested-by: Krishna Raman <kraman@xxxxxxxxxx> Signed-off-by: Samu Kallio <samu.kallio@xxxxxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1364045796-10720-1-git-send-email-konrad.wilk@xxxxxxxxxx Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- arch/x86/mm/fault.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -377,10 +377,12 @@ static noinline __kprobes int vmalloc_fa if (pgd_none(*pgd_ref)) return -1; - if (pgd_none(*pgd)) + if (pgd_none(*pgd)) { set_pgd(pgd, *pgd_ref); - else + arch_flush_lazy_mmu_mode(); + } else { BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); + } /* * Below here mismatches are bugs because these lower tables -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html