On Fri, Apr 28, 2017 at 2:39 PM, Jason Gunthorpe <[email protected]> wrote: > On Fri, Apr 28, 2017 at 02:32:31PM -0700, Josh Zimmerman wrote: >> On Fri, Apr 28, 2017 at 11:43 AM, Jason Gunthorpe >> <[email protected]> wrote: >> > On Fri, Apr 28, 2017 at 11:27:16AM -0700, Josh Zimmerman wrote: >> >> It sounds like there are several intertwined issues here. I'd like to >> >> keep this patch relatively minimal, so here are my current thoughts on >> >> a path forward: >> >> >> >> * Refactor references to chip->ops to go through tpm_try_get_ops, as >> >> mentioned in the previous patch >> > >> > As I said, if you rely on the fact that sysfs does not exist for TPM2 >> > then this should already be done for the TPM2 case and an incremental >> > later patch could solve this problem in sysfs to turn shutdown on for >> > tpm1. As long as this logic is clearly documented it is probably an OK >> > step for now. >> >> This I'm not actually sure about: it seems that there are other places >> than sysfs where chip->ops is referenced without being guarded by >> tpm_try_get_ops. If we rely on just NULLing out chip->ops this could >> be dangerous. I'll look at sending a patch for this first. > > If that is the case then we have an existing bug.. > > The only other user entry point is via the cdev, and those call > try_get_ops around all calls down into the tpm code. > > Everything coming in via the kapi must call tpm_chip_find_get, which > does try_get_ops.
OK, then I'm confused about the problem with sysfs. If everything is already grabbing a ref first, why can't we just grab a ref and NULL out chip->ops? My understanding from reading the other thread was that sysfs (and, possibly, some other places--see the paragraph starting "I went through the places that access chip->ops to see what's" in the original thread) doesn't grab the ref, which was part of the reason this was tricky. Josh ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ tpmdd-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/tpmdd-devel
