Messages in this thread | | | Date | Thu, 6 Apr 2023 17:58:59 -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 17:24, 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.
You mean compare known stat against current ? It seems more expensive to stat the file rather than using the simple i_version-has-changed indicator.
> > That sort of design may also eventually help IMA work properly with more > exotic filesystems, like NFS or Ceph.
And these don't support i_version at all?
Stefan
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