Re: [PATCH v3 1/3] [security] Add new hook to compare new mount to an existing mount
flat view
From: Paul Moore <paul@paul-moore.com>
Date: 2021-02-25 17:55:51
Also in:
linux-nfs, selinux
On Fri, Feb 19, 2021 at 5:25 PM Olga Kornievskaia [off-list ref] wrote:
From: Olga Kornievskaia <redacted> Add a new hook that takes an existing super block and a new mount with new options and determines if new options confict with an existing mount or not. A filesystem can use this new hook to determine if it can share the an existing superblock with a new superblock for the new mount. Signed-off-by: Olga Kornievskaia <redacted> --- include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 6 ++++ include/linux/security.h | 8 +++++ security/security.c | 7 +++++ security/selinux/hooks.c | 56 +++++++++++++++++++++++++++++++++++ 5 files changed, 78 insertions(+)
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diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index a19adef1f088..d76aaecfdf0f 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h@@ -142,6 +142,12 @@ * @orig the original mount data copied from userspace. * @copy copied data which will be passed to the security module. * Returns 0 if the copy was successful. + * @sb_mnt_opts_compat: + * Determine if the existing mount options are compatible with the new + * mount options being used.
Full disclosure: I'm a big fan of good documentation, regardless of if it lives in comments or a separate dedicated resource. Looking at the comment above, and the SELinux implementation of this hook below, it appears that the comment is a bit vague; specifically the use of "compatible". Based on the SELinux implementation, "compatible" would seem to equal, do you envision that to be the case for every LSM/security-model? If the answer is yes, then let's say that (and possibly rename the hook to "sb_mnt_opts_equal"). If the answer is no, then I think we need to do a better job explaining what compatibility really means; put yourself in the shoes of someone writing a LSM, what would they need to know to write an implementation for this hook?
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+ * @sb superblock being compared + * @mnt_opts new mount options + * Return 0 if options are compatible.
-- paul moore www.paul-moore.com