| Message ID | 20190413025541.20303-1-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/mmu: Fix an inverted list_empty() check when zapping sptes | expand |
On Fri, Apr 12, 2019 at 07:55:41PM -0700, Sean Christopherson wrote: > A recently introduced helper for handling zap vs. remote flush > incorrectly bails early, effectively leaking defunct shadow pages. > Manifests as a slab BUG when exiting KVM due to the shadow pages > being alive when their associated cache is destroyed. > > ========================================================================== > BUG kvm_mmu_page_header: Objects remaining in kvm_mmu_page_header on ... > -------------------------------------------------------------------------- > Disabling lock debugging due to kernel taint > INFO: Slab 0x00000000fc436387 objects=26 used=23 fp=0x00000000d023caee ... > CPU: 6 PID: 4315 Comm: rmmod Tainted: G B 5.1.0-rc2+ #19 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 > Call Trace: > dump_stack+0x46/0x5b > slab_err+0xad/0xd0 > ? on_each_cpu_mask+0x3c/0x50 > ? ksm_migrate_page+0x60/0x60 > ? on_each_cpu_cond_mask+0x7c/0xa0 > ? __kmalloc+0x1ca/0x1e0 > __kmem_cache_shutdown+0x13a/0x310 > shutdown_cache+0xf/0x130 > kmem_cache_destroy+0x1d5/0x200 > kvm_mmu_module_exit+0xa/0x30 [kvm] > kvm_arch_exit+0x45/0x60 [kvm] > kvm_exit+0x6f/0x80 [kvm] > vmx_exit+0x1a/0x50 [kvm_intel] > __x64_sys_delete_module+0x153/0x1f0 > ? exit_to_usermode_loop+0x88/0xc0 > do_syscall_64+0x4f/0x100 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Fixes: a21136345cb6f ("KVM: x86/mmu: Split remote_flush+zap case out of kvm_mmu_flush_or_zap()") > Cc: stable@vger.kernel.org Stable doesn't need to be Cc'd. I got my kernel versions mixed up, this bug only exists in 5.1. > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > arch/x86/kvm/mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index bd0727019674..e10962dfc203 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -2238,7 +2238,7 @@ static bool kvm_mmu_remote_flush_or_zap(struct kvm *kvm, > struct list_head *invalid_list, > bool remote_flush) > { > - if (!remote_flush && !list_empty(invalid_list)) > + if (!remote_flush && list_empty(invalid_list)) > return false; > > if (!list_empty(invalid_list)) > -- > 2.21.0 >
On 15/04/19 16:44, Sean Christopherson wrote: > On Fri, Apr 12, 2019 at 07:55:41PM -0700, Sean Christopherson wrote: >> A recently introduced helper for handling zap vs. remote flush >> incorrectly bails early, effectively leaking defunct shadow pages. >> Manifests as a slab BUG when exiting KVM due to the shadow pages >> being alive when their associated cache is destroyed. >> >> ========================================================================== >> BUG kvm_mmu_page_header: Objects remaining in kvm_mmu_page_header on ... >> -------------------------------------------------------------------------- >> Disabling lock debugging due to kernel taint >> INFO: Slab 0x00000000fc436387 objects=26 used=23 fp=0x00000000d023caee ... >> CPU: 6 PID: 4315 Comm: rmmod Tainted: G B 5.1.0-rc2+ #19 >> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 >> Call Trace: >> dump_stack+0x46/0x5b >> slab_err+0xad/0xd0 >> ? on_each_cpu_mask+0x3c/0x50 >> ? ksm_migrate_page+0x60/0x60 >> ? on_each_cpu_cond_mask+0x7c/0xa0 >> ? __kmalloc+0x1ca/0x1e0 >> __kmem_cache_shutdown+0x13a/0x310 >> shutdown_cache+0xf/0x130 >> kmem_cache_destroy+0x1d5/0x200 >> kvm_mmu_module_exit+0xa/0x30 [kvm] >> kvm_arch_exit+0x45/0x60 [kvm] >> kvm_exit+0x6f/0x80 [kvm] >> vmx_exit+0x1a/0x50 [kvm_intel] >> __x64_sys_delete_module+0x153/0x1f0 >> ? exit_to_usermode_loop+0x88/0xc0 >> do_syscall_64+0x4f/0x100 >> entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> >> Fixes: a21136345cb6f ("KVM: x86/mmu: Split remote_flush+zap case out of kvm_mmu_flush_or_zap()") >> Cc: stable@vger.kernel.org > > Stable doesn't need to be Cc'd. I got my kernel versions mixed up, this > bug only exists in 5.1. Indeed, I've already tested this and it seems to work fine (despite being a prime candidate for hiding other worse bugs :)). I will send the pull request to Linus either today or tomorrow. Paolo
========================================================================== BUG kvm_mmu_page_header: Objects remaining in kvm_mmu_page_header on ... -------------------------------------------------------------------------- Disabling lock debugging due to kernel taint INFO: Slab 0x00000000fc436387 objects=26 used=23 fp=0x00000000d023caee ... CPU: 6 PID: 4315 Comm: rmmod Tainted: G B 5.1.0-rc2+ #19 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: dump_stack+0x46/0x5b slab_err+0xad/0xd0 ? on_each_cpu_mask+0x3c/0x50 ? ksm_migrate_page+0x60/0x60 ? on_each_cpu_cond_mask+0x7c/0xa0 ? __kmalloc+0x1ca/0x1e0 __kmem_cache_shutdown+0x13a/0x310 shutdown_cache+0xf/0x130 kmem_cache_destroy+0x1d5/0x200 kvm_mmu_module_exit+0xa/0x30 [kvm] kvm_arch_exit+0x45/0x60 [kvm] kvm_exit+0x6f/0x80 [kvm] vmx_exit+0x1a/0x50 [kvm_intel] __x64_sys_delete_module+0x153/0x1f0 ? exit_to_usermode_loop+0x88/0xc0 do_syscall_64+0x4f/0x100 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: a21136345cb6f ("KVM: x86/mmu: Split remote_flush+zap case out of kvm_mmu_flush_or_zap()") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index bd0727019674..e10962dfc203 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2238,7 +2238,7 @@ static bool kvm_mmu_remote_flush_or_zap(struct kvm *kvm, struct list_head *invalid_list, bool remote_flush) { - if (!remote_flush && !list_empty(invalid_list)) + if (!remote_flush && list_empty(invalid_list)) return false; if (!list_empty(invalid_list))