On Wed, May 17, 2017 at 06:08:36PM +0900, AKASHI Takahiro wrote: > On Fri, May 12, 2017 at 05:59:23PM +0200, Luis R. Rodriguez wrote: > > On Fri, May 12, 2017 at 09:28:47AM +0900, AKASHI Takahiro wrote: > > > On Thu, May 11, 2017 at 11:32:30AM -0700, Luis R. Rodriguez wrote: > > > > On Thu, May 11, 2017 at 11:26 AM, Luis R. Rodriguez <[email protected]> > > > > wrote: > > > > > > > > > > It would seems to make sense to me to only need to verify files when > > > > > read > > > > > for the first time, once its cache I don't see why we would re-verify > > > > > them ? > > > > > > > > To be clear, the fw cache feature reads the files from the fs prior to > > > > suspend, and then uses the in-memory cache on resume. So it would make > > > > sense to me only to rely on fw verification on resume then when the fw > > > > cache is used ? > > > > > > Good point. I was thinking of need for verification on resume. > > > > From what we have discussed so far it would seem to me only necessary > > for a sig_check_ok (if we accept a file can have only one signature > > requirement) for a cache entry, and if its not set but a lookup needs > > a sig check it can do a full fs lookup. If such a lookup succeeded > > then it can fill the sig_check_ok in, provided the file contents > > match of course, given the file could have changed under the hood > > between the last file cache lookup (if the file did change that puts > > us at odd with the first lookup, but since its an update and no sig > > check is required, I guess it is fine to use its contents). > > > > > As cache is not protected > > > > Cache should be protected, it should be const and if its not we should fix > > that. > > Yeah, but > > > > and visible to the kernel, > > > > You mean it is visible to the kernel ? > > your current implementation doesn't provide any write protection.
The cache was implemented long ago by someone other than myself. Patches are welcomed. > > > some malware might want to rewrite it :) > > > > Right, we want to be pedantic about that sort of stuff and signature > > verification can help here but those benefits should carry their own > > weight. We should do what we can without file signature verification to > > protect the cache. > > > > The cache is short lived though, it exists only during suspend/resume. > > I found out why my test cases fail: > trigger_config_sync() in test_driver_data.c always enables REQ_KEEP flag > and so cached data (firmware_buf->data) has not been cleaned up. > I haven't fixed it in my test environment although I pointed it out before. Ah, perhaps the later revision of the test driver I posted captured this fix? > But the issue on write protection is still there wehn REQ_KEEP is used. Cache of firmware is a feature internal to the firmware_class, so it can only be fixed there. Patches welcomed. Luis
