Re: [Qemu-devel] [PATCH 5/5] pvrdma: check return value from pvrdma_idx_ring_has_ routines

[Yuval Shaia]

On Tue, Dec 11, 2018 at 06:56:42PM +0530, P J P wrote:
> From: Prasad J Pandit <address@hidden>
> 
> pvrdma_idx_ring_has_[data/space] routines also return invalid
> index PVRDMA_INVALID_IDX[=-1], if ring has no data/space. Check
> return value from these routines to avoid plausible infinite loops.
> 
> Reported-by: Li Qiang <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
>  hw/rdma/vmw/pvrdma_dev_ring.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/rdma/vmw/pvrdma_dev_ring.c b/hw/rdma/vmw/pvrdma_dev_ring.c
> index 01247fc041..61b6a0a869 100644
> --- a/hw/rdma/vmw/pvrdma_dev_ring.c
> +++ b/hw/rdma/vmw/pvrdma_dev_ring.c
> @@ -73,6 +73,7 @@ out:
>  
>  void *pvrdma_ring_next_elem_read(PvrdmaRing *ring)
>  {
> +    int e;
>      unsigned int idx = 0, offset;
>  
>      /*
> @@ -80,7 +81,8 @@ void *pvrdma_ring_next_elem_read(PvrdmaRing *ring)
>             ring->ring_state->cons_head);
>      */
>  
> -    if (!pvrdma_idx_ring_has_data(ring->ring_state, ring->max_elems, &idx)) {
> +    e = pvrdma_idx_ring_has_data(ring->ring_state, ring->max_elems, &idx);
> +    if (e <= 0) {
>          pr_dbg("No more data in ring\n");
>          return NULL;
>      }
> @@ -105,20 +107,24 @@ void pvrdma_ring_read_inc(PvrdmaRing *ring)
>  
>  void *pvrdma_ring_next_elem_write(PvrdmaRing *ring)
>  {
> -    unsigned int idx, offset, tail;
> +    int idx;
> +    unsigned int offset, tail;
>  
>      /*
>      pr_dbg("%s: t=%d, h=%d\n", ring->name, ring->ring_state->prod_tail,
>             ring->ring_state->cons_head);
>      */
> -
> -    if (!pvrdma_idx_ring_has_space(ring->ring_state, ring->max_elems, 
> &tail)) {
> +    idx = pvrdma_idx_ring_has_space(ring->ring_state, ring->max_elems, 
> &tail);
> +    if (idx <= 0) {
>          pr_dbg("CQ is full\n");
>          return NULL;
>      }
>  
>      idx = pvrdma_idx(&ring->ring_state->prod_tail, ring->max_elems);
> -    /* TODO: tail == idx */
> +    if (idx < 0 || tail == idx) {
> +        pr_dbg("invalid idx\n");
> +        return NULL;
> +    }

Thanks Prasad,
Two cosmetic suggestions though:
(1) In pvrdma_ring_next_elem_read, can you stick to your convention and
replace 'e' with 'idx'?
(2) Can you delete all leftover comments?

In any case:

Reviewed-by: Yuval Shaia <address@hidden>

>  
>      offset = idx * ring->elem_sz;
>      return ring->pages[offset / TARGET_PAGE_SIZE] + (offset % 
> TARGET_PAGE_SIZE);
> -- 
> 2.19.2
>