Messages in this thread | | | Date | Thu, 6 Apr 2023 18:27:16 -0400 | Subject | Re: [PATCH] overlayfs: Trigger file re-evaluation by IMA / EVM after writes | From | Stefan Berger <> |
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On 4/6/23 18:04, Jeff Layton wrote: > On Thu, 2023-04-06 at 17:24 -0400, Jeff Layton wrote: >> On Thu, 2023-04-06 at 16:22 -0400, Stefan Berger wrote: >>> >>> On 4/6/23 15:37, Jeff Layton wrote: >>>> On Thu, 2023-04-06 at 15:11 -0400, Stefan Berger wrote: >>>>> >>>>> On 4/6/23 14:46, Jeff Layton wrote: >>>>>> On Thu, 2023-04-06 at 17:01 +0200, Christian Brauner wrote: >>>>>>> On Thu, Apr 06, 2023 at 10:36:41AM -0400, Paul Moore wrote: >>>>> >>>>>> >>>>>> Correct. As long as IMA is also measuring the upper inode then it seems >>>>>> like you shouldn't need to do anything special here. >>>>> >>>>> Unfortunately IMA does not notice the changes. With the patch provided in the other email IMA works as expected. >>>>> >>>> >>>> >>>> It looks like remeasurement is usually done in ima_check_last_writer. >>>> That gets called from __fput which is called when we're releasing the >>>> last reference to the struct file. >>>> >>>> You've hooked into the ->release op, which gets called whenever >>>> filp_close is called, which happens when we're disassociating the file >>>> from the file descriptor table. >>>> >>>> So...I don't get it. Is ima_file_free not getting called on your file >>>> for some reason when you go to close it? It seems like that should be >>>> handling this. >>> >>> I would ditch the original proposal in favor of this 2-line patch shown here: >>> >>> https://lore.kernel.org/linux-integrity/a95f62ed-8b8a-38e5-e468-ecbde3b221af@linux.ibm.com/T/#m3bd047c6e5c8200df1d273c0ad551c645dd43232 >>> >>> >> >> Ok, I think I get it. IMA is trying to use the i_version from the >> overlayfs inode. >> >> I suspect that the real problem here is that IMA is just doing a bare >> inode_query_iversion. Really, we ought to make IMA call >> vfs_getattr_nosec (or something like it) to query the getattr routine in >> the upper layer. Then overlayfs could just propagate the results from >> the upper layer in its response. >> >> That sort of design may also eventually help IMA work properly with more >> exotic filesystems, like NFS or Ceph. >> >> >> > > Maybe something like this? It builds for me but I haven't tested it. It > looks like overlayfs already should report the upper layer's i_version > in getattr, though I haven't tested that either:
Thank you! I will give it a try once I am back.
Stefan
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