Am 12.07.2013 08:39, schrieb Dan Carpenter:
> My static checker marks everything from ntohl() as untrusted and it
> complains we could have an underflow problem doing:
>
> return (u32 *)&ary->wc_array[nchunks];
>
> Also on 32 bit systems the upper bound check could overflow.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_marshal.c b/net/sunrpc/xprtrdma/svc_rdma_marshal.c
> index 8d2eddd..65b1462 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_marshal.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_marshal.c
> @@ -98,6 +98,7 @@ void svc_rdma_rcl_chunk_counts(struct rpcrdma_read_chunk *ch,
> */
> static u32 *decode_write_list(u32 *va, u32 *vaend)
> {
> + unsigned long start, end;
> int nchunks;
>
> struct rpcrdma_write_array *ary =
> @@ -113,9 +114,12 @@ static u32 *decode_write_list(u32 *va, u32 *vaend)
> return NULL;
> }
> nchunks = ntohl(ary->wc_nchunks);
> - if (((unsigned long)&ary->wc_array[0] +
> - (sizeof(struct rpcrdma_write_chunk) * nchunks)) >
> - (unsigned long)vaend) {
> +
> + start = (unsigned long)&ary->wc_array[0];
> + end = (unsigned long)vaend;
> + if (nchunks < 0 ||
> + nchunks > (SIZE_MAX - start) / sizeof(struct rpcrdma_write_chunk) ||
> + (start + (sizeof(struct rpcrdma_write_chunk) * nchunks)) > end) {
> dprintk("svcrdma: ary=%p, wc_nchunks=%d, vaend=%p\n",
> ary, nchunks, vaend);
i am struggling to understand what is actually checked here.
Perhaps this improves the readability a bit
if ( nchunks < 0 ||
sizeof(struct rpcrdma_write_chunk) * nchunks > (SIZE_MAX - start) ||
sizeof(struct rpcrdma_write_chunk) * nchunks > (end - start) )
with that rewrite i would say that (SIZE_MAX - start) is strange.
just my 2 cents,
wh
> return NULL;
> @@ -129,6 +133,7 @@ static u32 *decode_write_list(u32 *va, u32 *vaend)
>
> static u32 *decode_reply_array(u32 *va, u32 *vaend)
> {
> + unsigned long start, end;
> int nchunks;
> struct rpcrdma_write_array *ary =
> (struct rpcrdma_write_array *)va;
> @@ -143,9 +148,12 @@ static u32 *decode_reply_array(u32 *va, u32 *vaend)
> return NULL;
> }
> nchunks = ntohl(ary->wc_nchunks);
> - if (((unsigned long)&ary->wc_array[0] +
> - (sizeof(struct rpcrdma_write_chunk) * nchunks)) >
> - (unsigned long)vaend) {
> +
> + start = (unsigned long)&ary->wc_array[0];
> + end = (unsigned long)vaend;
> + if (nchunks < 0 ||
> + nchunks > (SIZE_MAX - start) / sizeof(struct rpcrdma_write_chunk) ||
> + (start + (sizeof(struct rpcrdma_write_chunk) * nchunks)) > end) {
> dprintk("svcrdma: ary=%p, wc_nchunks=%d, vaend=%p\n",
> ary, nchunks, vaend);
> return NULL;
> --
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