linux-kernel - Re: [PATCH v3 0/5] Smack transmute fixes

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Date: Wed, 24 Jan 2024 14:31:10 -0800
From: Casey Schaufler <casey@...aufler-ca.com>
To: Roberto Sassu <roberto.sassu@...weicloud.com>, paul@...l-moore.com,
 jmorris@...ei.org, serge@...lyn.com
Cc: linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
 Roberto Sassu <roberto.sassu@...wei.com>,
 Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v3 0/5] Smack transmute fixes

On 11/16/2023 1:01 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.com>
>
> The first two patches are obvious fixes, the first restricts setting the
> SMACK64TRANSMUTE xattr only for directories, and the second makes it
> possible to set SMACK64TRANSMUTE if the filesystem does not support xattrs
> (e.g. ramfs).
>
> The remaining fixes are optional, and only required if we want filesystems
> without xattr support behave like those with xattr support. Since we have
> the inode_setsecurity and inode_getsecurity hooks to make the first group
> work, it seems useful to fix inode creation too (SELinux should be fine).
>
> The third patch is merely a code move out of the 'if (xattr)' condition.
> The fourth updates the security field of the in-memory inode directly in
> smack_inode_init_security() and marks the inode as instantiated,

I have taken patches 1-4 in smack-next. I'm still waiting on a convincing
approval for patch 5.


>  and the
> fifth adds a security_inode_init_security() call in ramfs to initialize the
> security field of the in-memory inodes (needed to test transmuting
> directories).
>
> Both the Smack (on xfs) and IMA test suite succeed with all patches
> applied. Tests were not executed on v3 (trivial changes).
>
> By executing the tests in a ramfs, the results are:
>
> Without the patches:
> 86 Passed, 9 Failed, 90% Success rate
>
> With the patches:
> 93 Passed, 2 Failed, 97% Success rate
>
> The remaining two failures are:
> 2151  ioctl(4, BTRFS_IOC_CLONE or FICLONE, 3) = -1 EOPNOTSUPP (Operation not supported)
> 2152  lsetxattr("./targets/proc-attr-Snap", "security.SMACK64EXEC", "Pop", 3, 0) = -1 EOPNOTSUPP (Operation not supported)
>
> The first one is likely due ramfs lack of support for ioctl() while the
> second could be fixed by handling SMACK64EXEC in smack_inode_setsecurity().
>
> The patch set applies on top of lsm/dev, commit e246777e2a03 ("MAINTAINERS:
> update the LSM entry").
>
> The ramfs patch potentially could be useful to correctly initialize the
> label of new inodes in the initramfs, assuming that it will be fully
> labeled with support for xattrs in the cpio image:
>
> https://lore.kernel.org/linux-integrity/20190523121803.21638-1-roberto.sassu@huawei.com/
>
> Ramfs inode labels will be set from xattrs with the inode_setsecurity hook.
>
> Changelog
>
> v2:
> - Replace return with goto in the ramfs patch, for better maintainability
>   (suggested by Andrew Morton)
>
> v1:
> - Rebase on top of latest lsm/next
> - Remove -EOPNOTSUPP check in patch 5 (cannot happen)
>
> Roberto Sassu (5):
>   smack: Set SMACK64TRANSMUTE only for dirs in smack_inode_setxattr()
>   smack: Handle SMACK64TRANSMUTE in smack_inode_setsecurity()
>   smack: Always determine inode labels in smack_inode_init_security()
>   smack: Initialize the in-memory inode in smack_inode_init_security()
>   ramfs: Initialize security of in-memory inodes
>
>  fs/ramfs/inode.c           | 32 ++++++++++++-
>  security/smack/smack_lsm.c | 95 ++++++++++++++++++++++----------------
>  2 files changed, 86 insertions(+), 41 deletions(-)
>