da(4): defend against calling sysctl_ctx_free on unininitalized sysctl_ctx

[Nate Lawson]

On Tue, 7 Oct 2003, Thomas Quinot wrote:
> The following change resolves a recently observed panic on probe of
> various USB mass storage devices. It is similar to the one I committed
> in scsi_cd.c rev 1.86. Please review!
>
> Thanks,
> Thomas.
>
> Index: scsi_da.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/cam/scsi/scsi_da.c,v
> retrieving revision 1.159
> diff -u -r1.159 scsi_da.c
> --- scsi_da.c	4 Sep 2003 01:01:20 -0000	1.159
> +++ scsi_da.c	7 Oct 2003 14:48:26 -0000
> @@ -89,7 +89,8 @@
>  	DA_FLAG_NEED_OTAG	= 0x020,
>  	DA_FLAG_WENT_IDLE	= 0x040,
>  	DA_FLAG_RETRY_UA	= 0x080,
> -	DA_FLAG_OPEN		= 0x100
> +	DA_FLAG_OPEN		= 0x100,
> +	DA_FLAG_SCTX_INIT	= 0x200
>  } da_flags;
>
>  typedef enum {
> @@ -838,7 +839,8 @@
>  	/*
>  	 * If we can't free the sysctl tree, oh well...
>  	 */
> -	if (sysctl_ctx_free(&softc->sysctl_ctx) != 0) {
> +	if ((softc->flags & DA_FLAG_SCTX_INIT) != 0
> +	    && sysctl_ctx_free(&softc->sysctl_ctx) != 0) {
>  		xpt_print_path(periph->path);
>  		printf("can't remove sysctl context\n");
>  	}
> @@ -925,6 +927,7 @@
>
>  	mtx_lock(&Giant);
>  	sysctl_ctx_init(&softc->sysctl_ctx);
> +	softc->flags |= DA_FLAG_SCTX_INIT;
>  	softc->sysctl_tree = SYSCTL_ADD_NODE(&softc->sysctl_ctx,
>  		SYSCTL_STATIC_CHILDREN(_kern_cam_da), OID_AUTO, tmpstr2,
>  		CTLFLAG_RD, 0, tmpstr);

I'm ok with committing this, thanks for running it by me.  Perhaps there's
a better way to signal whether the sysctl has been initialized though.
Perhaps a check for SYSCTL_CHILDREN != NULL or something?  I've fought
with sysctl already this week and I'm not sure how to do that.

-Nate