| Message ID | 20230125083851.27759-5-surenb@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | introduce vm_flags modifier functions | expand |
On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote: > Replace indirect modifications to vma->vm_flags with calls to modifier > functions to be able to track flag changes and to keep vma locking > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > vm_flags modification attempts. Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I gueess we should be willing to trust it. > Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Michal Hocko <mhocko@suse.com>
On Wed, Jan 25, 2023 at 1:38 AM 'Michal Hocko' via kernel-team <kernel-team@android.com> wrote: > > On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote: > > Replace indirect modifications to vma->vm_flags with calls to modifier > > functions to be able to track flag changes and to keep vma locking > > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > > vm_flags modification attempts. > > Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I > gueess we should be willing to trust it. Yes, but I really want to prevent an indirect misuse since it was not easy to find these. If you feel strongly about it I will remove them or if you have a better suggestion I'm all for it. > > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > > Acked-by: Michal Hocko <mhocko@suse.com> > -- > Michal Hocko > SUSE Labs > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >
On Wed 25-01-23 08:57:48, Suren Baghdasaryan wrote: > On Wed, Jan 25, 2023 at 1:38 AM 'Michal Hocko' via kernel-team > <kernel-team@android.com> wrote: > > > > On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote: > > > Replace indirect modifications to vma->vm_flags with calls to modifier > > > functions to be able to track flag changes and to keep vma locking > > > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > > > vm_flags modification attempts. > > > > Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I > > gueess we should be willing to trust it. > > Yes, but I really want to prevent an indirect misuse since it was not > easy to find these. If you feel strongly about it I will remove them > or if you have a better suggestion I'm all for it. You can avoid that by making flags inaccesible directly, right?
On Wed, Jan 25, 2023 at 9:08 AM Michal Hocko <mhocko@suse.com> wrote: > > On Wed 25-01-23 08:57:48, Suren Baghdasaryan wrote: > > On Wed, Jan 25, 2023 at 1:38 AM 'Michal Hocko' via kernel-team > > <kernel-team@android.com> wrote: > > > > > > On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote: > > > > Replace indirect modifications to vma->vm_flags with calls to modifier > > > > functions to be able to track flag changes and to keep vma locking > > > > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > > > > vm_flags modification attempts. > > > > > > Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I > > > gueess we should be willing to trust it. > > > > Yes, but I really want to prevent an indirect misuse since it was not > > easy to find these. If you feel strongly about it I will remove them > > or if you have a better suggestion I'm all for it. > > You can avoid that by making flags inaccesible directly, right? Ah, you mean Peter's suggestion of using __private? I guess that would cover it. I'll drop these BUG_ONs in the next version. Thanks! > > -- > Michal Hocko > SUSE Labs
On Wed, Jan 25, 2023 at 12:38:49AM -0800, Suren Baghdasaryan wrote: > Replace indirect modifications to vma->vm_flags with calls to modifier > functions to be able to track flag changes and to keep vma locking > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > vm_flags modification attempts. > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org> > --- > arch/powerpc/kvm/book3s_hv_uvmem.c | 5 ++++- > arch/s390/mm/gmap.c | 5 ++++- > mm/khugepaged.c | 2 ++ > mm/ksm.c | 2 ++ > 4 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c > index 1d67baa5557a..325a7a47d348 100644 > --- a/arch/powerpc/kvm/book3s_hv_uvmem.c > +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c > @@ -393,6 +393,7 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm, > { > unsigned long gfn = memslot->base_gfn; > unsigned long end, start = gfn_to_hva(kvm, gfn); > + unsigned long vm_flags; > int ret = 0; > struct vm_area_struct *vma; > int merge_flag = (merge) ? MADV_MERGEABLE : MADV_UNMERGEABLE; > @@ -409,12 +410,14 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm, > ret = H_STATE; > break; > } > + vm_flags = vma->vm_flags; > ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, > - merge_flag, &vma->vm_flags); > + merge_flag, &vm_flags); > if (ret) { > ret = H_STATE; > break; > } > + reset_vm_flags(vma, vm_flags); > start = vma->vm_end; > } while (end > vma->vm_end); > > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c > index 3a695b8a1e3c..d5eb47dcdacb 100644 > --- a/arch/s390/mm/gmap.c > +++ b/arch/s390/mm/gmap.c > @@ -2587,14 +2587,17 @@ int gmap_mark_unmergeable(void) > { > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > + unsigned long vm_flags; > int ret; > VMA_ITERATOR(vmi, mm, 0); > > for_each_vma(vmi, vma) { > + vm_flags = vma->vm_flags; > ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, > - MADV_UNMERGEABLE, &vma->vm_flags); > + MADV_UNMERGEABLE, &vm_flags); > if (ret) > return ret; > + reset_vm_flags(vma, vm_flags); > } > mm->def_flags &= ~VM_MERGEABLE; > return 0; > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 8abc59345bf2..76b24cd0c179 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -354,6 +354,8 @@ struct attribute_group khugepaged_attr_group = { > int hugepage_madvise(struct vm_area_struct *vma, > unsigned long *vm_flags, int advice) > { > + /* vma->vm_flags can be changed only using modifier functions */ > + BUG_ON(vm_flags == &vma->vm_flags); > switch (advice) { > case MADV_HUGEPAGE: > #ifdef CONFIG_S390 > diff --git a/mm/ksm.c b/mm/ksm.c > index 04f1c8c2df11..992b2be9f5e6 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -2573,6 +2573,8 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start, > struct mm_struct *mm = vma->vm_mm; > int err; > > + /* vma->vm_flags can be changed only using modifier functions */ > + BUG_ON(vm_flags == &vma->vm_flags); > switch (advice) { > case MADV_MERGEABLE: > /* > -- > 2.39.1 > >
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c index 1d67baa5557a..325a7a47d348 100644 --- a/arch/powerpc/kvm/book3s_hv_uvmem.c +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c @@ -393,6 +393,7 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm, { unsigned long gfn = memslot->base_gfn; unsigned long end, start = gfn_to_hva(kvm, gfn); + unsigned long vm_flags; int ret = 0; struct vm_area_struct *vma; int merge_flag = (merge) ? MADV_MERGEABLE : MADV_UNMERGEABLE; @@ -409,12 +410,14 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm, ret = H_STATE; break; } + vm_flags = vma->vm_flags; ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, - merge_flag, &vma->vm_flags); + merge_flag, &vm_flags); if (ret) { ret = H_STATE; break; } + reset_vm_flags(vma, vm_flags); start = vma->vm_end; } while (end > vma->vm_end); diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index 3a695b8a1e3c..d5eb47dcdacb 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -2587,14 +2587,17 @@ int gmap_mark_unmergeable(void) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; + unsigned long vm_flags; int ret; VMA_ITERATOR(vmi, mm, 0); for_each_vma(vmi, vma) { + vm_flags = vma->vm_flags; ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, - MADV_UNMERGEABLE, &vma->vm_flags); + MADV_UNMERGEABLE, &vm_flags); if (ret) return ret; + reset_vm_flags(vma, vm_flags); } mm->def_flags &= ~VM_MERGEABLE; return 0; diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 8abc59345bf2..76b24cd0c179 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -354,6 +354,8 @@ struct attribute_group khugepaged_attr_group = { int hugepage_madvise(struct vm_area_struct *vma, unsigned long *vm_flags, int advice) { + /* vma->vm_flags can be changed only using modifier functions */ + BUG_ON(vm_flags == &vma->vm_flags); switch (advice) { case MADV_HUGEPAGE: #ifdef CONFIG_S390 diff --git a/mm/ksm.c b/mm/ksm.c index 04f1c8c2df11..992b2be9f5e6 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2573,6 +2573,8 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start, struct mm_struct *mm = vma->vm_mm; int err; + /* vma->vm_flags can be changed only using modifier functions */ + BUG_ON(vm_flags == &vma->vm_flags); switch (advice) { case MADV_MERGEABLE: /*
Replace indirect modifications to vma->vm_flags with calls to modifier functions to be able to track flag changes and to keep vma locking correctness. Add a BUG_ON check in ksm_madvise() to catch indirect vm_flags modification attempts. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- arch/powerpc/kvm/book3s_hv_uvmem.c | 5 ++++- arch/s390/mm/gmap.c | 5 ++++- mm/khugepaged.c | 2 ++ mm/ksm.c | 2 ++ 4 files changed, 12 insertions(+), 2 deletions(-)