From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Farman Subject: Re: [PATCH v3 1/6] vfio-ccw: make it safe to access channel programs Date: Tue, 5 Feb 2019 09:41:15 -0500 Message-ID: <34836353-1c5b-4013-f0ff-6172bf493618@linux.ibm.com> References: <20190130132212.7376-1-cohuck@redhat.com> <20190130132212.7376-2-cohuck@redhat.com> <9b35717e-8994-cde9-2afe-243ab80c371a@linux.ibm.com> <20190205130344.30b8279f.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-s390@vger.kernel.org, Alex Williamson , Pierre Morel , kvm@vger.kernel.org, Farhan Ali , qemu-devel@nongnu.org, Halil Pasic , qemu-s390x@nongnu.org To: Cornelia Huck Return-path: In-Reply-To: <20190205130344.30b8279f.cohuck@redhat.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On 02/05/2019 07:03 AM, Cornelia Huck wrote: > On Mon, 4 Feb 2019 14:25:34 -0500 > Eric Farman wrote: > >> On 01/30/2019 08:22 AM, Cornelia Huck wrote: >>> When we get a solicited interrupt, the start function may have >>> been cleared by a csch, but we still have a channel program >>> structure allocated. Make it safe to call the cp accessors in >>> any case, so we can call them unconditionally. >>> >>> While at it, also make sure that functions called from other parts >>> of the code return gracefully if the channel program structure >>> has not been initialized (even though that is a bug in the caller). >>> >>> Signed-off-by: Cornelia Huck >>> --- >>> drivers/s390/cio/vfio_ccw_cp.c | 20 +++++++++++++++++++- >>> drivers/s390/cio/vfio_ccw_cp.h | 2 ++ >>> drivers/s390/cio/vfio_ccw_fsm.c | 5 +++++ >>> 3 files changed, 26 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c >>> index ba08fe137c2e..0bc0c38edda7 100644 >>> --- a/drivers/s390/cio/vfio_ccw_cp.c >>> +++ b/drivers/s390/cio/vfio_ccw_cp.c >>> @@ -335,6 +335,7 @@ static void cp_unpin_free(struct channel_program *cp) >>> struct ccwchain *chain, *temp; >>> int i; >>> >>> + cp->initialized = false; >>> list_for_each_entry_safe(chain, temp, &cp->ccwchain_list, next) { >>> for (i = 0; i < chain->ch_len; i++) { >>> pfn_array_table_unpin_free(chain->ch_pat + i, >>> @@ -701,6 +702,8 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb) >>> */ >>> cp->orb.cmd.c64 = 1; >>> >>> + cp->initialized = true; >>> + >> >> Not seen in this hunk, but we call ccwchain_loop_tic() just prior to >> this point. If that returns non-zero, we call cp_unpin_free()[1] (and >> set initailized to false), and then fall through to here. So this is >> going to set initialized to true, even though we're taking an error >> path. :-( > > Eek, setting c64 unconditionally threw me off. This needs to check > for !ret, of course. > >> >> [1] Wait, why is it calling cp_unpin_free()? Oh, I had proposed >> squashing cp_free() and cp_unpin_free() back in November[2], got an r-b >> from Pierre but haven't gotten back to tidy up the series for a v2. >> Okay, I'll try to do that again soon. :-) > > :) > >> [2] https://patchwork.kernel.org/patch/10675261/ >> >>> return ret; >>> } >>> >>> @@ -715,7 +718,8 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb) >>> */ >>> void cp_free(struct channel_program *cp) >>> { >>> - cp_unpin_free(cp); >>> + if (cp->initialized) >>> + cp_unpin_free(cp); >>> } >>> >>> /** >>> @@ -760,6 +764,10 @@ int cp_prefetch(struct channel_program *cp) >>> struct ccwchain *chain; >>> int len, idx, ret; >>> >>> + /* this is an error in the caller */ >>> + if (!cp || !cp->initialized) >>> + return -EINVAL; >>> + >>> list_for_each_entry(chain, &cp->ccwchain_list, next) { >>> len = chain->ch_len; >>> for (idx = 0; idx < len; idx++) { >>> @@ -795,6 +803,10 @@ union orb *cp_get_orb(struct channel_program *cp, u32 intparm, u8 lpm) >>> struct ccwchain *chain; >>> struct ccw1 *cpa; >>> >>> + /* this is an error in the caller */ >>> + if (!cp || !cp->initialized) >>> + return NULL; >>> + >>> orb = &cp->orb; >>> >>> orb->cmd.intparm = intparm; >>> @@ -831,6 +843,9 @@ void cp_update_scsw(struct channel_program *cp, union scsw *scsw) >>> u32 cpa = scsw->cmd.cpa; >>> u32 ccw_head, ccw_tail; >>> >>> + if (!cp->initialized) >>> + return; >>> + >>> /* >>> * LATER: >>> * For now, only update the cmd.cpa part. We may need to deal with >>> @@ -869,6 +884,9 @@ bool cp_iova_pinned(struct channel_program *cp, u64 iova) >>> struct ccwchain *chain; >>> int i; >>> >>> + if (!cp->initialized) >> >> So, two of the checks added above look for a nonzero cp pointer prior to >> checking initialized, while two don't. I guess cp can't be NULL, since >> it's embedded in the private struct directly and that's only free'd when >> we do vfio_ccw_sch_remove() ... But I guess some consistency in how we >> look would be nice. > > The idea was: In which context is this called? Is there a legitimate > reason for the caller to pass in an uninitialized cp, or would that > mean the caller had messed up (and we should not trust cp to be !NULL > either?) > > But you're right, that does look inconsistent. Always checking for > cp != NULL probably looks least odd, although it is overkill. Opinions? My opinion? Since cp is embedded in vfio_ccw_private, rather than a pointer to a separately malloc'd struct, we pass &private->cp to those functions. So a check for !cp doesn't really buy us anything because what we are actually concerned about is whether or not private is NULL, which only changes on the probe/remove boundaries. > >> >>> + return false; >>> + >>> list_for_each_entry(chain, &cp->ccwchain_list, next) { >>> for (i = 0; i < chain->ch_len; i++) >>> if (pfn_array_table_iova_pinned(chain->ch_pat + i, >