Re: [Qemu-devel] [PATCH v1] qemu-pr-helper: garbage response structure can be used to write data

[Stefan Hajnoczi]

On Fri, Jun 15, 2018 at 12:11:44PM +0300, Dima Stepanov wrote:
> The prh_co_entry() routine handles requests. The first part is to read a
> request by calling the prh_read_request() routine, if:
>   1. scsi_cdb_xfer(req->cdb) call returns 0, and
>   2. req->cdb[0] == PERSISTENT_RESERVE_IN, then
> The resp->result field will be uninitialized. As a result the resp.sz
> field will be also uninitialized in the prh_co_entry() function.
> The second part is to send the response by calling the
> prh_write_response() routine:
>   1. For the PERSISTENT_RESERVE_IN command, and
>   2. resp->result == GOOD (previous successful reply or just luck), then
> There is a probability that the following assert will not be trigered:
>   assert(resp->sz <= req->sz && resp->sz <= sizeof(client->data));
> As a result some uninitialized response will be sent.
> 
> The fix is to initialize the response structure to CHECK_CONDITION and 0
> values before calling the prh_read_request() routine.
> 
> Signed-off-by: Dima Stepanov <address@hidden>
> ---
>  scsi/qemu-pr-helper.c | 2 ++
>  1 file changed, 2 insertions(+)

CCing Paolo Bonzini, SCSI maintainer.

You can use scripts/get_maintainer.pl -f scsi/qemu-pr-helper.c to find
relevant people to CC on a patch.

> 
> diff --git a/scsi/qemu-pr-helper.c b/scsi/qemu-pr-helper.c
> index d0f8317..85878c2 100644
> --- a/scsi/qemu-pr-helper.c
> +++ b/scsi/qemu-pr-helper.c
> @@ -768,6 +768,8 @@ static void coroutine_fn prh_co_entry(void *opaque)
>          PRHelperResponse resp;
>          int sz;
>  
> +        resp.result = CHECK_CONDITION;
> +        resp.sz = 0;
>          sz = prh_read_request(client, &req, &resp, &local_err);
>          if (sz < 0) {
>              break;
> -- 
> 2.7.4
> 
>

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