Re: [Patch 3/4] ipc/mqueue: strengthen checks on mqueue creation

KOSAKI Motohiro
2012-05-01T20:01:57Z

(5/1/12 1:50 PM), Doug Ledford wrote:
> We already check the mq attr struct if it's passed in, but now that the
> admin can set system wide defaults separate from maximums, it's actually
> possible to set the defaults to something that would overflow. So,
> if there is no attr struct passed in to the open call, check the default
> values.
>
> While we are at it, simplify mq_attr_ok() by making it return 0 or an
> error condition, so that way if we add more tests to it later, we have
> the option of what error should be returned instead of the calling
> location having to pick a possibly inaccurate error code.
>
> Signed-off-by: Doug Ledford<dledford@redhat.com>
> ---
> ipc/mqueue.c | 27 ++++++++++++++++++---------
> 1 files changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/ipc/mqueue.c b/ipc/mqueue.c
> index 4b2892e..6089f73 100644
> --- a/ipc/mqueue.c
> +++ b/ipc/mqueue.c
> @@ -673,27 +673,27 @@ static int mq_attr_ok(struct ipc_namespace *ipc_ns, struct mq_attr *attr)
> int mq_treesize;
>
> if (attr->mq_maxmsg<= 0 || attr->mq_msgsize<= 0)
> - return 0;
> + return -EINVAL;
> if (capable(CAP_SYS_RESOURCE)) {
> if (attr->mq_maxmsg> HARD_MSGMAX ||
> attr->mq_msgsize> HARD_MSGSIZEMAX)
> - return 0;
> + return -EINVAL;
> } else {
> if (attr->mq_maxmsg> ipc_ns->mq_msg_max ||
> attr->mq_msgsize> ipc_ns->mq_msgsize_max)
> - return 0;
> + return -EINVAL;
> }
> /* check for overflow */
> if (attr->mq_msgsize> ULONG_MAX/attr->mq_maxmsg)
> - return 0;
> + return -ENOMEM;
> mq_treesize = attr->mq_maxmsg * sizeof(struct msg_msg) +
> min_t(unsigned int, attr->mq_maxmsg, MQ_PRIO_MAX) *
> sizeof(struct posix_msg_tree_node);
> if ((unsigned long)(attr->mq_maxmsg * attr->mq_msgsize +
> mq_treesize)<
> (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize))
> - return 0;
> - return 1;
> + return -ENOMEM;
> + return 0;

But ENOMEM is more inaccurate. It almostly is used for kmalloc failure.