On Wed, 2023-03-08 at 10:14 -0500, Mimi Zohar wrote: > Hi Roberto, > > On Fri, 2023-03-03 at 19:18 +0100, Roberto Sassu wrote: > > From: Roberto Sassu <roberto.sassu@xxxxxxxxxx> > > > > This patch set depends on: > > - https://lore.kernel.org/linux-integrity/20221201104125.919483-1-roberto.sassu@xxxxxxxxxxxxxxx/ (there will be a v8 shortly) > > - https://lore.kernel.org/linux-security-module/20230217032625.678457-1-paul@xxxxxxxxxxxxxx/ > > > > IMA and EVM are not effectively LSMs, especially due the fact that in the > > past they could not provide a security blob while there is another LSM > > active. > > > > That changed in the recent years, the LSM stacking feature now makes it > > possible to stack together multiple LSMs, and allows them to provide a > > security blob for most kernel objects. While the LSM stacking feature has > > some limitations being worked out, it is already suitable to make IMA and > > EVM as LSMs. > > > > In short, while this patch set is big, it does not make any functional > > change to IMA and EVM. IMA and EVM functions are called by the LSM > > infrastructure in the same places as before (except ima_post_path_mknod()), > > rather being hardcoded calls, and the inode metadata pointer is directly > > stored in the inode security blob rather than in a separate rbtree. > > > > More specifically, patches 1-13 make IMA and EVM functions suitable to > > be registered to the LSM infrastructure, by aligning function parameters. > > > > Patches 14-22 add new LSM hooks in the same places where IMA and EVM > > functions are called, if there is no LSM hook already. > > > > Patch 23 adds the 'last' ordering strategy for LSMs, so that IMA and EVM > > functions are called in the same order as of today. Also, like with the > > 'first' strategy, LSMs using it are always enabled, so IMA and EVM > > functions will be always called (if IMA and EVM are compiled built-in). > > > > Patches 24-27 do the bulk of the work, remove hardcoded calls to IMA and > > EVM functions, register those functions in the LSM infrastructure, and let > > the latter call them. In addition, they also reserve one slot for EVM to > > supply an xattr to the inode_init_security hook. > > > > Finally, patch 28 removes the rbtree used to bind metadata to the inodes, > > and instead reserve a space in the inode security blob to store the pointer > > to metadata. This also brings performance improvements due to retrieving > > metadata in constant time, as opposed to logarithmic. > > Prior to IMA being upstreamed, it went through a number of iterations, > first on the security hooks, then as a separate parallel set of > integrity hooks, and, finally, co-located with the security hooks, > where they exist. With this patch set we've come full circle. > > With the LSM stacking support, multiple LSMs can now use the > 'i_security' field removing the need for the rbtree indirection for > accessing integrity state info. > > Roberto, thank you for making this change. Mostly it looks good. > Reviewing the patch set will be easier once the prereq's and this patch > set can be properly applied. Welcome. Yes, once Paul reviews the other patch set, we can progressively apply the patches. Thanks Roberto
