[Xen-devel] [PATCH] acm: fix deadlock and bogus loop (Was Re: [Xen-changelog] [xen-unstable] acm: Further fixes after grant-table changes.)

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

acm: fix deadlock and bogus loop.

It is very likly to overlook the outside loop.
    for ( pd = &domain_list; *pd != NULL; pd = &(*pd)->next_in_list ) {
        ...
        spin_lock(&(*pd)->grant_table->lock);
        for ( i = 0; i < nr_grant_entries((*pd)->grant_table); i++ ) {
                ...
        }
        spin_unlock(&(*pd)->grant_table->lock); <<< necessary
    }
    out_gnttab:
    spin_unlock(&(*pd)->grant_table->lock); <<< bogus


On Mon, Feb 19, 2007 at 05:20:09PM -0800, Xen patchbot-unstable wrote:
> # HG changeset patch
> # User kfraser@xxxxxxxxxxxxxxxxxxxxx
> # Date 1171901134 0
> # Node ID 184db7a674d93d92d0d963a7b3c80f1889983a9e
> # Parent  3b7bdb7bd1303eff6db3e223fc5bb8d06c86c570
> acm: Further fixes after grant-table changes.
> Based on a patch from Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
> Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
> ---
>  xen/acm/acm_simple_type_enforcement_hooks.c |   20 ++++++++++----------
>  1 files changed, 10 insertions(+), 10 deletions(-)
> 
> diff -r 3b7bdb7bd130 -r 184db7a674d9 
> xen/acm/acm_simple_type_enforcement_hooks.c
> --- a/xen/acm/acm_simple_type_enforcement_hooks.c     Mon Feb 19 15:52:51 
> 2007 +0000
> +++ b/xen/acm/acm_simple_type_enforcement_hooks.c     Mon Feb 19 16:05:34 
> 2007 +0000
> @@ -177,7 +177,7 @@ ste_init_state(struct acm_ste_policy_buf
>      ssidref_t ste_ssidref, ste_rssidref;
>      struct domain **pd, *rdom;
>      domid_t rdomid;
> -    struct grant_entry *sha_copy;
> +    struct grant_entry sha_copy;
>      int port, i;
>  
>      read_lock(&domlist_lock); /* go by domain? or directly by global? 
> event/grant list */
> @@ -234,20 +234,18 @@ ste_init_state(struct acm_ste_policy_buf
>              }
>          } 
>          /* b) check for grant table conflicts on shared pages */
> -        if ((*pd)->grant_table->shared == NULL) {
> -            printkd("%s: Grant ... sharing for domain %x not setup!\n", 
> __func__, (*pd)->domain_id);
> -            continue;
> -        }
> +        spin_lock(&(*pd)->grant_table->lock);
>          for ( i = 0; i < nr_grant_frames((*pd)->grant_table); i++ ) {
> -            sha_copy =  (*pd)->grant_table->shared[i];
> -            if ( sha_copy->flags ) {
> +#define SPP (PAGE_SIZE / sizeof(struct grant_entry))
> +            sha_copy = (*pd)->grant_table->shared[i/SPP][i%SPP];
> +            if ( sha_copy.flags ) {
>                  printkd("%s: grant dom (%hu) SHARED (%d) flags:(%hx) 
> dom:(%hu) frame:(%lx)\n",
>                          __func__, (*pd)->domain_id, i, sha_copy.flags, 
> sha_copy.domid, 
>                          (unsigned long)sha_copy.frame);
> -                rdomid = sha_copy->domid;
> +                rdomid = sha_copy.domid;
>                  if ((rdom = get_domain_by_id(rdomid)) == NULL) {
>                      printkd("%s: domain not found ERROR!\n", __func__);
> -                    goto out;
> +                    goto out_gnttab;
>                  };
>                  /* rdom now has remote domain */
>                  ste_rssid = GET_SSIDP(ACM_SIMPLE_TYPE_ENFORCEMENT_POLICY, 
> @@ -257,12 +255,14 @@ ste_init_state(struct acm_ste_policy_buf
>                  if (!have_common_type(ste_ssidref, ste_rssidref)) {
>                      printkd("%s: Policy violation in grant table sharing 
> domain %x -> domain %x.\n",
>                              __func__, (*pd)->domain_id, rdomid);
> -                    goto out;
> +                    goto out_gnttab;
>                  }
>              }
>          }
>      }
>      violation = 0;
> + out_gnttab:
> +    spin_unlock(&(*pd)->grant_table->lock);
>   out:
>      read_unlock(&domlist_lock);
>      return violation;
> 
> _______________________________________________
> Xen-changelog mailing list
> Xen-changelog@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-changelog
> 

-- 
yamahata

Attachment: 13997_fe78383d8218_acm_fix_13991.patch
Description: Text Data

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