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

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Message-ID: <91852af1-eb93-7740-850a-35e5dce9915d@schaufler-ca.com>
Date:   Wed, 7 Jun 2023 07:53:27 -0700
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: [RFC][PATCH 0/5] Smack transmute fixes

On 6/7/2023 5:36 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, 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.
>
> By setting the ROOT variable to a ramfs mountpoint, 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:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm.git/log/?h=next
>
> plus:
>
> https://github.com/cschaufler/smack-next/commits/next
>
> plus:
>
> https://lore.kernel.org/linux-integrity/20230603191518.1397490-1-roberto.sassu@huaweicloud.com/
>
> 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.
>
> 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           | 27 +++++++++++
>  security/smack/smack_lsm.c | 93 ++++++++++++++++++++++----------------
>  2 files changed, 82 insertions(+), 38 deletions(-)

I will run these through my test cycle, but they look good at first glance.
Thank you.