Re: [Xen-devel] [PATCH] xen/xsm: Fix xsm_mmu_* and xsm_update_va_mapping hooks

[Stephen Smalley <sds@xxxxxxxxxxxxx>]

On Mon, 2011-03-21 at 14:57 -0400, Stephen Smalley wrote:
> This is an attempt to properly fix the hypervisor crash previously
> described in
> http://marc.info/?l=xen-devel&m=128396289707362&w=2
> 
> In looking into this issue, I think the proper fix is to move the
> xsm_mmu_* and xsm_update_va_mapping hook calls later in the callers,
> after more validation has been performed and the page_info struct is
> readily available, and pass the page_info to the hooks. This patch moves
> the xsm_mmu_normal_update, xsm_mmu_machphys_update and
> xsm_update_va_mapping hook calls accordingly, and updates their
> interfaces and hook function implementations.  This appears to resolve
> the crashes for me.  However, as I am not overly familiar with this area
> of code, I'd appreciate any feedback or suggestions for improvement.
> 
> Signed-off-by:  Stephen Smalley <sds@xxxxxxxxxxxxx>

Zero replies after two postings.  Should I retry, abort, or fail?
Seriously though - if there is something wrong with this patch, then let
me know, and if not, can it get applied sometime?

> ---
> 
>  xen/arch/x86/mm.c     |   29 ++++++++++++++++++-----------
>  xen/include/xsm/xsm.h |   28 +++++++++++++++-------------
>  xen/xsm/dummy.c       |   11 ++++++-----
>  xen/xsm/flask/hooks.c |   41 ++++++++---------------------------------
>  4 files changed, 47 insertions(+), 62 deletions(-)
> 
> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -3448,9 +3448,6 @@
>          {
>              p2m_type_t p2mt;
>  
> -            rc = xsm_mmu_normal_update(d, pg_owner, req.val);
> -            if ( rc )
> -                break;
>              rc = -EINVAL;
>  
>              req.ptr -= cmd;
> @@ -3478,6 +3475,13 @@
>                            (unsigned long)(req.ptr & ~PAGE_MASK));
>              page = mfn_to_page(mfn);
>  
> +            rc = xsm_mmu_normal_update(d, req.val, page);
> +            if ( rc ) {
> +                unmap_domain_page_with_cache(va, &mapcache);
> +                put_page(page);
> +                break;
> +            }
> +
>              if ( page_lock(page) )
>              {
>                  switch ( page->u.inuse.type_info & PGT_type_mask )
> @@ -3640,10 +3644,6 @@
>              mfn = req.ptr >> PAGE_SHIFT;
>              gpfn = req.val;
>  
> -            rc = xsm_mmu_machphys_update(d, mfn);
> -            if ( rc )
> -                break;
> -
>              if ( unlikely(!get_page_from_pagenr(mfn, pg_owner)) )
>              {
>                  MEM_LOG("Could not get page for mach->phys update");
> @@ -3658,6 +3658,10 @@
>                  break;
>              }
>  
> +            rc = xsm_mmu_machphys_update(d, mfn_to_page(mfn));
> +            if ( rc )
> +                break;
> +
>              set_gpfn_from_mfn(mfn, gpfn);
>  
>              paging_mark_dirty(pg_owner, mfn);
> @@ -4272,10 +4276,6 @@
>  
>      perfc_incr(calls_to_update_va);
>  
> -    rc = xsm_update_va_mapping(d, pg_owner, val);
> -    if ( rc )
> -        return rc;
> -
>      rc = -EINVAL;
>      pl1e = guest_map_l1e(v, va, &gl1mfn);
>      if ( unlikely(!pl1e || !get_page_from_pagenr(gl1mfn, d)) )
> @@ -4295,6 +4295,13 @@
>          goto out;
>      }
>  
> +    rc = xsm_update_va_mapping(d, val, gl1pg);
> +    if ( rc ) {
> +        page_unlock(gl1pg);
> +        put_page(gl1pg);
> +        goto out;
> +    }
> +
>      rc = mod_l1_entry(pl1e, val, gl1mfn, 0, v, pg_owner);
>  
>      page_unlock(gl1pg);
> diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
> --- a/xen/include/xsm/xsm.h
> +++ b/xen/include/xsm/xsm.h
> @@ -136,11 +136,12 @@
>      int (*getidletime) (void);
>      int (*machine_memory_map) (void);
>      int (*domain_memory_map) (struct domain *d);
> -    int (*mmu_normal_update) (struct domain *d, struct domain *f, 
> -                                                                intpte_t 
> fpte);
> -    int (*mmu_machphys_update) (struct domain *d, unsigned long mfn);
> -    int (*update_va_mapping) (struct domain *d, struct domain *f, 
> -                                                            l1_pgentry_t 
> pte);
> +    int (*mmu_normal_update) (struct domain *d,
> +                           intpte_t fpte, struct page_info *page);
> +    int (*mmu_machphys_update) (struct domain *d, struct page_info *page);
> +    int (*update_va_mapping) (struct domain *d,
> +                           l1_pgentry_t pte,
> +                           struct page_info *page);
>      int (*add_to_physmap) (struct domain *d1, struct domain *d2);
>      int (*sendtrigger) (struct domain *d);
>      int (*test_assign_device) (uint32_t machine_bdf);
> @@ -567,21 +568,22 @@
>      return xsm_call(domain_memory_map(d));
>  }
>  
> -static inline int xsm_mmu_normal_update (struct domain *d, struct domain *f, 
> -                                                                intpte_t 
> fpte)
> +static inline int xsm_mmu_normal_update (struct domain *d,
> +                                      intpte_t fpte, struct page_info *page)
>  {
> -    return xsm_call(mmu_normal_update(d, f, fpte));
> +    return xsm_call(mmu_normal_update(d, fpte, page));
>  }
>  
> -static inline int xsm_mmu_machphys_update (struct domain *d, unsigned long 
> mfn)
> +static inline int xsm_mmu_machphys_update (struct domain *d, struct 
> page_info *page)
>  {
> -    return xsm_call(mmu_machphys_update(d, mfn));
> +    return xsm_call(mmu_machphys_update(d, page));
>  }
>  
> -static inline int xsm_update_va_mapping(struct domain *d, struct domain *f, 
> -                                                            l1_pgentry_t pte)
> +static inline int xsm_update_va_mapping(struct domain *d,
> +                                     l1_pgentry_t pte,
> +                                     struct page_info *page)
>  {
> -    return xsm_call(update_va_mapping(d, f, pte));
> +    return xsm_call(update_va_mapping(d, pte, page));
>  }
>  
>  static inline int xsm_add_to_physmap(struct domain *d1, struct domain *d2)
> diff --git a/xen/xsm/dummy.c b/xen/xsm/dummy.c
> --- a/xen/xsm/dummy.c
> +++ b/xen/xsm/dummy.c
> @@ -405,19 +405,20 @@
>      return 0;
>  }
>  
> -static int dummy_mmu_normal_update (struct domain *d, struct domain *f, 
> -                                                                intpte_t 
> fpte)
> +static int dummy_mmu_normal_update (struct domain *d,
> +                                 intpte_t fpte, struct page_info *page)
>  {
>      return 0;
>  }
>  
> -static int dummy_mmu_machphys_update (struct domain *d, unsigned long mfn)
> +static int dummy_mmu_machphys_update (struct domain *d, struct page_info 
> *page)
>  {
>      return 0;
>  }
>  
> -static int dummy_update_va_mapping (struct domain *d, struct domain *f, 
> -                                                            l1_pgentry_t pte)
> +static int dummy_update_va_mapping (struct domain *d,
> +                                 l1_pgentry_t pte,
> +                                 struct page_info *page)
>  {
>      return 0;
>  }
> diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
> --- a/xen/xsm/flask/hooks.c
> +++ b/xen/xsm/flask/hooks.c
> @@ -347,26 +347,6 @@
>      return rc;
>  }
>  
> -static int get_mfn_sid(unsigned long mfn, u32 *sid)
> -{
> -    int rc = 0;
> -    struct page_info *page;
> -
> -    if ( mfn_valid(mfn) )
> -    {
> -        /*mfn is valid if this is a page that Xen is tracking!*/
> -        page = mfn_to_page(mfn);
> -        rc = get_page_sid(page, sid);
> -    }
> -    else
> -    {
> -        /*Possibly an untracked IO page?*/
> -        rc = security_iomem_sid(mfn, sid);
> -    }
> -
> -    return rc;    
> -}
> -
>  static int flask_memory_adjust_reservation(struct domain *d1, struct domain 
> *d2)
>  {
>      return domain_has_perm(d1, d2, SECCLASS_MMU, MMU__ADJUST);
> @@ -1006,12 +986,11 @@
>      return domain_has_perm(current->domain, d, SECCLASS_MMU, MMU__MEMORYMAP);
>  }
>  
> -static int flask_mmu_normal_update(struct domain *d, struct domain *f, 
> -                                   intpte_t fpte)
> +static int flask_mmu_normal_update(struct domain *d, 
> +                                   intpte_t fpte, struct page_info *page)
>  {
>      int rc = 0;
>      u32 map_perms = MMU__MAP_READ;
> -    unsigned long fmfn;
>      struct domain_security_struct *dsec;
>      u32 fsid;
>  
> @@ -1020,42 +999,38 @@
>      if ( l1e_get_flags(l1e_from_intpte(fpte)) & _PAGE_RW )
>          map_perms |= MMU__MAP_WRITE;
>  
> -    fmfn = gmfn_to_mfn(f, l1e_get_pfn(l1e_from_intpte(fpte)));
> -
> -    rc = get_mfn_sid(fmfn, &fsid);
> +    rc = get_page_sid(page, &fsid);
>      if ( rc )
>          return rc;
>  
>      return avc_has_perm(dsec->sid, fsid, SECCLASS_MMU, map_perms, NULL);
>  }
>  
> -static int flask_mmu_machphys_update(struct domain *d, unsigned long mfn)
> +static int flask_mmu_machphys_update(struct domain *d, struct page_info 
> *page)
>  {
>      int rc = 0;
>      u32 psid;
>      struct domain_security_struct *dsec;
>      dsec = d->ssid;
>  
> -    rc = get_mfn_sid(mfn, &psid);
> +    rc = get_page_sid(page, &psid);
>      if ( rc )
>          return rc;
>  
>      return avc_has_perm(dsec->sid, psid, SECCLASS_MMU, MMU__UPDATEMP, NULL);
>  }
>  
> -static int flask_update_va_mapping(struct domain *d, struct domain *f, 
> -                                   l1_pgentry_t pte)
> +static int flask_update_va_mapping(struct domain *d,
> +                                   l1_pgentry_t pte, struct page_info *page)
>  {
>      int rc = 0;
>      u32 psid;
>      u32 map_perms = MMU__MAP_READ;
> -    unsigned long mfn;
>      struct domain_security_struct *dsec;
>  
>      dsec = d->ssid;
>  
> -    mfn = gmfn_to_mfn(f, l1e_get_pfn(pte));        
> -    rc = get_mfn_sid(mfn, &psid);
> +    rc = get_page_sid(page, &psid);
>      if ( rc )
>          return rc;
>  
> 

-- 
Stephen Smalley
National Security Agency


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