From: "Mickaël Salaün" <mic@digikod.net>
To: "Günther Noack" <gnoack3000@gmail.com>,
linux-security-module@vger.kernel.org
Cc: James Morris <jmorris@namei.org>,
Paul Moore <paul@paul-moore.com>,
"Serge E . Hallyn" <serge@hallyn.com>,
linux-fsdevel@vger.kernel.org,
Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Subject: Re: [PATCH v8 3/9] landlock: Refactor check_access_path_dual() into is_access_to_paths_allowed()
Date: Wed, 5 Oct 2022 20:54:08 +0200 [thread overview]
Message-ID: <16f036ca-fd68-2e89-2ceb-0b9e211a4b23@digikod.net> (raw)
In-Reply-To: <20221001154908.49665-4-gnoack3000@gmail.com>
Great!
On 01/10/2022 17:49, Günther Noack wrote:
> * Rename it to is_access_to_paths_allowed()
> * Make it return true iff the access is allowed
> * Calculate the EXDEV/EACCES error code in the one place where it's needed
Can you please replace these bullet points with (one-sentence) paragraphs?
>
> Suggested-by: Mickaël Salaün <mic@digikod.net>
> Signed-off-by: Günther Noack <gnoack3000@gmail.com>
> ---
> security/landlock/fs.c | 89 +++++++++++++++++++++---------------------
> 1 file changed, 44 insertions(+), 45 deletions(-)
>
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index a9dbd99d9ee7..083dd3d359de 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -430,7 +430,7 @@ is_eacces(const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS],
> }
>
> /**
> - * check_access_path_dual - Check accesses for requests with a common path
> + * is_access_to_paths_allowed - Check accesses for requests with a common path
> *
> * @domain: Domain to check against.
> * @path: File hierarchy to walk through.
> @@ -465,14 +465,10 @@ is_eacces(const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS],
> * allow the request.
> *
> * Returns:
> - * - 0 if the access request is granted;
> - * - -EACCES if it is denied because of access right other than
> - * LANDLOCK_ACCESS_FS_REFER;
> - * - -EXDEV if the renaming or linking would be a privileged escalation
> - * (according to each layered policies), or if LANDLOCK_ACCESS_FS_REFER is
> - * not allowed by the source or the destination.
> + * - true if the access request is granted;
> + * - false otherwise
Missing final dot.
> */
> -static int check_access_path_dual(
> +static bool is_access_to_paths_allowed(
> const struct landlock_ruleset *const domain,
> const struct path *const path,
> const access_mask_t access_request_parent1,
> @@ -492,17 +488,17 @@ static int check_access_path_dual(
> (*layer_masks_child2)[LANDLOCK_NUM_ACCESS_FS] = NULL;
>
> if (!access_request_parent1 && !access_request_parent2)
> - return 0;
> + return true;
> if (WARN_ON_ONCE(!domain || !path))
> - return 0;
> + return true;
> if (is_nouser_or_private(path->dentry))
> - return 0;
> + return true;
> if (WARN_ON_ONCE(domain->num_layers < 1 || !layer_masks_parent1))
> - return -EACCES;
> + return false;
>
> if (unlikely(layer_masks_parent2)) {
> if (WARN_ON_ONCE(!dentry_child1))
> - return -EACCES;
> + return false;
> /*
> * For a double request, first check for potential privilege
> * escalation by looking at domain handled accesses (which are
> @@ -513,7 +509,7 @@ static int check_access_path_dual(
> is_dom_check = true;
> } else {
> if (WARN_ON_ONCE(dentry_child1 || dentry_child2))
> - return -EACCES;
> + return false;
> /* For a simple request, only check for requested accesses. */
> access_masked_parent1 = access_request_parent1;
> access_masked_parent2 = access_request_parent2;
> @@ -622,24 +618,7 @@ static int check_access_path_dual(
> }
> path_put(&walker_path);
>
> - if (allowed_parent1 && allowed_parent2)
> - return 0;
> -
> - /*
> - * This prioritizes EACCES over EXDEV for all actions, including
> - * renames with RENAME_EXCHANGE.
> - */
> - if (likely(is_eacces(layer_masks_parent1, access_request_parent1) ||
> - is_eacces(layer_masks_parent2, access_request_parent2)))
> - return -EACCES;
> -
> - /*
> - * Gracefully forbids reparenting if the destination directory
> - * hierarchy is not a superset of restrictions of the source directory
> - * hierarchy, or if LANDLOCK_ACCESS_FS_REFER is not allowed by the
> - * source or the destination.
> - */
> - return -EXDEV;
> + return allowed_parent1 && allowed_parent2;
> }
>
> static inline int check_access_path(const struct landlock_ruleset *const domain,
> @@ -649,8 +628,10 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
> layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
>
> access_request = init_layer_masks(domain, access_request, &layer_masks);
> - return check_access_path_dual(domain, path, access_request,
> - &layer_masks, NULL, 0, NULL, NULL);
> + if (is_access_to_paths_allowed(domain, path, access_request,
> + &layer_masks, NULL, 0, NULL, NULL))
> + return 0;
> + return -EACCES;
> }
>
> static inline int current_check_access_path(const struct path *const path,
> @@ -711,8 +692,9 @@ static inline access_mask_t maybe_remove(const struct dentry *const dentry)
> * file. While walking from @dir to @mnt_root, we record all the domain's
> * allowed accesses in @layer_masks_dom.
> *
> - * This is similar to check_access_path_dual() but much simpler because it only
> - * handles walking on the same mount point and only check one set of accesses.
> + * This is similar to is_access_to_paths_allowed() but much simpler because it
> + * only handles walking on the same mount point and only checks one set of
> + * accesses.
> *
> * Returns:
> * - true if all the domain access rights are allowed for @dir;
> @@ -857,10 +839,11 @@ static int current_check_refer_path(struct dentry *const old_dentry,
> access_request_parent1 = init_layer_masks(
> dom, access_request_parent1 | access_request_parent2,
> &layer_masks_parent1);
> - return check_access_path_dual(dom, new_dir,
> - access_request_parent1,
> - &layer_masks_parent1, NULL, 0,
> - NULL, NULL);
> + if (is_access_to_paths_allowed(
> + dom, new_dir, access_request_parent1,
> + &layer_masks_parent1, NULL, 0, NULL, NULL))
> + return 0;
> + return -EACCES;
> }
>
> access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER;
> @@ -886,11 +869,27 @@ static int current_check_refer_path(struct dentry *const old_dentry,
> * parent access rights. This will be useful to compare with the
> * destination parent access rights.
> */
> - return check_access_path_dual(dom, &mnt_dir, access_request_parent1,
> - &layer_masks_parent1, old_dentry,
> - access_request_parent2,
> - &layer_masks_parent2,
> - exchange ? new_dentry : NULL);
> + if (is_access_to_paths_allowed(
> + dom, &mnt_dir, access_request_parent1, &layer_masks_parent1,
> + old_dentry, access_request_parent2, &layer_masks_parent2,
> + exchange ? new_dentry : NULL))
> + return 0;
> +
> + /*
> + * This prioritizes EACCES over EXDEV for all actions, including
> + * renames with RENAME_EXCHANGE.
> + */
> + if (likely(is_eacces(&layer_masks_parent1, access_request_parent1) ||
> + is_eacces(&layer_masks_parent2, access_request_parent2)))
> + return -EACCES;
> +
> + /*
> + * Gracefully forbids reparenting if the destination directory
> + * hierarchy is not a superset of restrictions of the source directory
> + * hierarchy, or if LANDLOCK_ACCESS_FS_REFER is not allowed by the
> + * source or the destination.
> + */
> + return -EXDEV;
> }
>
> /* Inode hooks */
next prev parent reply other threads:[~2022-10-05 18:54 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-01 15:48 [PATCH v8 0/9] landlock: truncate support Günther Noack
2022-10-01 15:49 ` [PATCH v8 1/9] security: Create file_truncate hook from path_truncate hook Günther Noack
2022-10-05 18:53 ` Mickaël Salaün
2022-10-08 7:45 ` Günther Noack
2022-10-06 1:10 ` Paul Moore
2022-10-01 15:49 ` [PATCH v8 2/9] selftests/landlock: Locally define __maybe_unused Günther Noack
2022-10-05 18:53 ` Mickaël Salaün
2022-10-08 7:47 ` Günther Noack
2022-10-01 15:49 ` [PATCH v8 3/9] landlock: Refactor check_access_path_dual() into is_access_to_paths_allowed() Günther Noack
2022-10-05 18:54 ` Mickaël Salaün [this message]
2022-10-08 7:54 ` Günther Noack
2022-10-01 15:49 ` [PATCH v8 4/9] landlock: Support file truncation Günther Noack
2022-10-04 19:56 ` Nathan Chancellor
2022-10-05 18:52 ` Mickaël Salaün
2022-10-06 20:19 ` Günther Noack
2022-10-05 18:55 ` Mickaël Salaün
2022-10-08 8:08 ` Günther Noack
2022-10-01 15:49 ` [PATCH v8 5/9] selftests/landlock: Selftests for file truncation support Günther Noack
2022-10-01 15:49 ` [PATCH v8 6/9] selftests/landlock: Test open() and ftruncate() in multiple scenarios Günther Noack
2022-10-05 18:56 ` Mickaël Salaün
2022-10-01 15:49 ` [PATCH v8 7/9] selftests/landlock: Test FD passing from a Landlock-restricted to an unrestricted process Günther Noack
2022-10-05 18:57 ` Mickaël Salaün
2022-10-08 8:25 ` Günther Noack
2022-10-01 15:49 ` [PATCH v8 8/9] samples/landlock: Extend sample tool to support LANDLOCK_ACCESS_FS_TRUNCATE Günther Noack
2022-10-05 18:57 ` Mickaël Salaün
2022-10-08 8:47 ` Günther Noack
2022-10-01 15:49 ` [PATCH v8 9/9] landlock: Document Landlock's file truncation support Günther Noack
2022-10-05 18:57 ` Mickaël Salaün
2022-10-08 8:49 ` Günther Noack
2022-10-05 19:18 ` [PATCH v8 0/9] landlock: truncate support Mickaël Salaün
2022-10-08 10:20 ` Günther Noack
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=16f036ca-fd68-2e89-2ceb-0b9e211a4b23@digikod.net \
--to=mic@digikod.net \
--cc=gnoack3000@gmail.com \
--cc=jmorris@namei.org \
--cc=konstantin.meskhidze@huawei.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=paul@paul-moore.com \
--cc=serge@hallyn.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).