Re: [Xen-devel] [PATCH 2/2] xen-blkfront: implement safe version of llist_for_each_entry

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Dec 04, 2012 at 03:21:53PM +0100, Roger Pau Monne wrote:
> Implement a safe version of llist_for_each_entry, and use it in
> blkif_free. Previously grants where freed while iterating the list,
> which lead to dereferences when trying to fetch the next item.

Looks like xen-blkfront is the only user of this llist_for_each_entry.

Would it be more prudent to put the macro in the llist.h file?

> 
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxx
> ---
>  drivers/block/xen-blkfront.c |   10 +++++++++-
>  1 files changed, 9 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 96e9b00..df21b05 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -143,6 +143,13 @@ static DEFINE_SPINLOCK(minor_lock);
>  
>  #define DEV_NAME     "xvd"   /* name in /dev */
>  
> +#define llist_for_each_entry_safe(pos, n, node, member)              \
> +     for ((pos) = llist_entry((node), typeof(*(pos)), member),       \
> +          (n) = (pos)->member.next;                                  \
> +          &(pos)->member != NULL;                                    \
> +          (pos) = llist_entry(n, typeof(*(pos)), member),            \
> +          (n) = (&(pos)->member != NULL) ? (pos)->member.next : NULL)
> +
>  static int get_id_from_freelist(struct blkfront_info *info)
>  {
>       unsigned long free = info->shadow_free;
> @@ -792,6 +799,7 @@ static void blkif_free(struct blkfront_info *info, int 
> suspend)
>  {
>       struct llist_node *all_gnts;
>       struct grant *persistent_gnt;
> +     struct llist_node *n;
>  
>       /* Prevent new requests being issued until we fix things up. */
>       spin_lock_irq(&info->io_lock);
> @@ -804,7 +812,7 @@ static void blkif_free(struct blkfront_info *info, int 
> suspend)
>       /* Remove all persistent grants */
>       if (info->persistent_gnts_c) {
>               all_gnts = llist_del_all(&info->persistent_gnts);
> -             llist_for_each_entry(persistent_gnt, all_gnts, node) {
> +             llist_for_each_entry_safe(persistent_gnt, n, all_gnts, node) {
>                       gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
>                       __free_page(pfn_to_page(persistent_gnt->pfn));
>                       kfree(persistent_gnt);
> -- 
> 1.7.7.5 (Apple Git-26)
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel