Hi: Response below ... On 11/13/2015 11:15 AM, Lee Duncan wrote: > On 10/28/2015 06:28 AM, FUJITA Tomonori wrote: >> On Mon, 19 Oct 2015 08:56:06 -0700 >> Lee Duncan <lduncan@xxxxxxxx> wrote: >> >>> On 10/17/2015 05:57 AM, FUJITA Tomonori wrote: >>>> On Tue, 13 Oct 2015 11:10:17 -0700 >>>> Lee Duncan <lduncan@xxxxxxxx> wrote: >>>> >>>>> Hello: >>>>> >>>>> I recently got a report of a tgtd core dump from our opencloud >>>>> group. The stack trace showed that a strcmp against a NULL was causing >>>>> the failure: >>>>> >>>>> ... >>>>> >>>>> It looks like target_find_by_name() uses tgt_targetname(), but doesn't >>>>> account for the fact that it can return a NULL when the target being >>>>> looked up does not (now) exist: >>>> >>>> Thanks for theI supplied a patch you appliedI supplied a patch you applied patch. But I'm confused why this happens. target with >>>> the same tid as iscsi_target must exist? >>>> >>> >>> No, I believe this is happening because the targets are getting >>> dynamically removed. But I will verify that. Because if tgt_targetname() >>> can return a NULL (as apparently it did this time), there are probably >>> other places in the code that need to check for that. >> >> Ok, I'm still confused but applied the patch. Let's see if it would >> help. >> >> Thanks, > > I am still trying to look more deeply into how this could happen. > > This bug was triggered when using cloud storage as the back-end for for > their target, and that cloud storage "goes away". (I am still trying to > determine what that actually means.) If so, I should be able to simulate > by allowing my back-end storage to go away. > > As you say, let's see if we see any other instances of tgt_targetname() > returning null, in other spots in the code. > I thought that you might like to know that I finally tested this. I created a test bed where I randomly created and deleted 4 target nodes by changing the configuration files then running "tgt-admin --update ALL -f". At the same time, I randomly attempted to log out of then back into all 4 targets. It only takes a minute to hit the case the patch I sent fixes, where target_find_by_name() dies when tgt_targetname() returns an unexpected NULL. It was nice to validate that the patch was actually needed. You might remember, though, that I was worried that other places where tgt_targetname() where used might need to check for NULL as well. So I tested for that. Surprisingly, none of the other places that uses tgt_targetname() ever got NULL back. I tested for several hours. So either I just didn't hit the corner case needed to tickle such a bug, or that just doesn't happen. I would love to investigate further, but I may not have the time to get to it soon. In the mean time, it appears we are in good shape. -- Lee Duncan -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
