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From: David Howells <dhowells@redhat.com>
To: linux-cachefs@redhat.com
Cc: dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Jeff Layton <jlayton@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Omar Sandoval <osandov@osandov.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
	linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
	v9fs-developer@lists.sourceforge.net,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 35/64] cachefiles: Add security derivation
Date: Mon, 29 Nov 2021 14:31:14 +0000	[thread overview]
Message-ID: <163819627469.215744.3603633690679962985.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <163819575444.215744.318477214576928110.stgit@warthog.procyon.org.uk>


---

 fs/cachefiles/Makefile   |    3 +
 fs/cachefiles/internal.h |   20 ++++++++
 fs/cachefiles/security.c |  112 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 134 insertions(+), 1 deletion(-)
 create mode 100644 fs/cachefiles/security.c

diff --git a/fs/cachefiles/Makefile b/fs/cachefiles/Makefile
index 183fb5f3b8b1..28bbb0d14868 100644
--- a/fs/cachefiles/Makefile
+++ b/fs/cachefiles/Makefile
@@ -4,7 +4,8 @@
 #
 
 cachefiles-y := \
-	main.o
+	main.o \
+	security.o
 
 cachefiles-$(CONFIG_CACHEFILES_ERROR_INJECTION) += error_inject.o
 
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index b2adcb59b4ce..e57ce5ef875c 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -104,6 +104,26 @@ static inline int cachefiles_inject_remove_error(void)
 	return cachefiles_error_injection_state & 2 ? -EIO : 0;
 }
 
+/*
+ * security.c
+ */
+extern int cachefiles_get_security_ID(struct cachefiles_cache *cache);
+extern int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
+					       struct dentry *root,
+					       const struct cred **_saved_cred);
+
+static inline void cachefiles_begin_secure(struct cachefiles_cache *cache,
+					   const struct cred **_saved_cred)
+{
+	*_saved_cred = override_creds(cache->cache_cred);
+}
+
+static inline void cachefiles_end_secure(struct cachefiles_cache *cache,
+					 const struct cred *saved_cred)
+{
+	revert_creds(saved_cred);
+}
+
 /*
  * Error handling
  */
diff --git a/fs/cachefiles/security.c b/fs/cachefiles/security.c
new file mode 100644
index 000000000000..fe777164f1d8
--- /dev/null
+++ b/fs/cachefiles/security.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* CacheFiles security management
+ *
+ * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/fs.h>
+#include <linux/cred.h>
+#include "internal.h"
+
+/*
+ * determine the security context within which we access the cache from within
+ * the kernel
+ */
+int cachefiles_get_security_ID(struct cachefiles_cache *cache)
+{
+	struct cred *new;
+	int ret;
+
+	_enter("{%s}", cache->secctx);
+
+	new = prepare_kernel_cred(current);
+	if (!new) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	if (cache->secctx) {
+		ret = set_security_override_from_ctx(new, cache->secctx);
+		if (ret < 0) {
+			put_cred(new);
+			pr_err("Security denies permission to nominate security context: error %d\n",
+			       ret);
+			goto error;
+		}
+	}
+
+	cache->cache_cred = new;
+	ret = 0;
+error:
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * see if mkdir and create can be performed in the root directory
+ */
+static int cachefiles_check_cache_dir(struct cachefiles_cache *cache,
+				      struct dentry *root)
+{
+	int ret;
+
+	ret = security_inode_mkdir(d_backing_inode(root), root, 0);
+	if (ret < 0) {
+		pr_err("Security denies permission to make dirs: error %d",
+		       ret);
+		return ret;
+	}
+
+	ret = security_inode_create(d_backing_inode(root), root, 0);
+	if (ret < 0)
+		pr_err("Security denies permission to create files: error %d",
+		       ret);
+
+	return ret;
+}
+
+/*
+ * check the security details of the on-disk cache
+ * - must be called with security override in force
+ * - must return with a security override in force - even in the case of an
+ *   error
+ */
+int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
+					struct dentry *root,
+					const struct cred **_saved_cred)
+{
+	struct cred *new;
+	int ret;
+
+	_enter("");
+
+	/* duplicate the cache creds for COW (the override is currently in
+	 * force, so we can use prepare_creds() to do this) */
+	new = prepare_creds();
+	if (!new)
+		return -ENOMEM;
+
+	cachefiles_end_secure(cache, *_saved_cred);
+
+	/* use the cache root dir's security context as the basis with
+	 * which create files */
+	ret = set_create_files_as(new, d_backing_inode(root));
+	if (ret < 0) {
+		abort_creds(new);
+		cachefiles_begin_secure(cache, _saved_cred);
+		_leave(" = %d [cfa]", ret);
+		return ret;
+	}
+
+	put_cred(cache->cache_cred);
+	cache->cache_cred = new;
+
+	cachefiles_begin_secure(cache, _saved_cred);
+	ret = cachefiles_check_cache_dir(cache, root);
+
+	if (ret == -EOPNOTSUPP)
+		ret = 0;
+	_leave(" = %d", ret);
+	return ret;
+}



  parent reply	other threads:[~2021-11-29 14:33 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-29 14:22 [PATCH 00/64] fscache, cachefiles: Rewrite David Howells
2021-11-29 14:22 ` [PATCH 01/64] fscache, cachefiles: Disable configuration David Howells
2021-11-29 14:22 ` [PATCH 02/64] cachefiles: Delete the cachefiles driver pending rewrite David Howells
2021-11-29 14:23 ` [PATCH 03/64] fscache: Remove the contents of the fscache driver, " David Howells
2021-11-29 14:23 ` [PATCH 04/64] netfs: Display the netfs inode number in the netfs_read tracepoint David Howells
2021-11-29 14:23 ` [PATCH 05/64] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space David Howells
2021-11-29 14:24 ` [PATCH 06/64] fscache: Introduce new driver David Howells
2021-11-29 14:24 ` [PATCH 07/64] fscache: Implement a hash function David Howells
2021-11-29 14:24 ` [PATCH 08/64] fscache: Implement cache registration David Howells
2021-11-29 14:24 ` [PATCH 09/64] fscache: Implement volume registration David Howells
2021-11-29 14:25 ` [PATCH 10/64] fscache: Implement cookie registration David Howells
2021-11-29 14:25 ` [PATCH 11/64] fscache: Implement cache-level access helpers David Howells
2021-11-29 14:25 ` [PATCH 12/64] fscache: Implement volume-level " David Howells
2021-11-29 14:25 ` [PATCH 13/64] fscache: Implement cookie-level " David Howells
2021-11-29 14:26 ` [PATCH 14/64] fscache: Implement functions add/remove a cache David Howells
2021-11-29 14:26 ` [PATCH 15/64] fscache: Provide and use cache methods to lookup/create/free a volume David Howells
2021-11-29 14:26 ` [PATCH 16/64] fscache: Add a function for a cache backend to note an I/O error David Howells
2021-11-29 14:26 ` [PATCH 17/64] fscache: Implement simple cookie state machine David Howells
2021-11-29 14:26 ` [PATCH 18/64] fscache: Implement cookie user counting and resource pinning David Howells
2021-11-29 14:27 ` [PATCH 19/64] fscache: Implement cookie invalidation David Howells
2021-11-29 14:27 ` [PATCH 20/64] fscache: Provide a means to begin an operation David Howells
2021-11-29 14:28 ` [PATCH 21/64] fscache: Count data storage objects in a cache David Howells
2021-11-29 14:28 ` [PATCH 22/64] fscache: Provide read/write stat counters for the cache David Howells
2021-11-29 14:28 ` [PATCH 23/64] fscache: Provide a function to let the netfs update its coherency data David Howells
2021-11-29 14:28 ` [PATCH 24/64] netfs: Pass more information on how to deal with a hole in the cache David Howells
2021-12-06 11:42   ` JeffleXu
2021-12-09 16:49   ` David Howells
2021-11-29 14:28 ` [PATCH 25/64] fscache: Implement raw I/O interface David Howells
2021-11-29 14:29 ` [PATCH 26/64] fscache: Implement higher-level write " David Howells
2021-11-29 14:29 ` [PATCH 27/64] vfs, fscache: Implement pinning of cache usage for writeback David Howells
2021-11-29 14:29 ` [PATCH 28/64] fscache: Provide a function to note the release of a page David Howells
2021-11-29 14:30 ` [PATCH 29/64] fscache: Provide a function to resize a cookie David Howells
2021-11-29 14:30 ` [PATCH 30/64] cachefiles: Introduce rewritten driver David Howells
2021-11-29 14:30 ` [PATCH 31/64] cachefiles: Define structs David Howells
2021-11-29 14:30 ` [PATCH 32/64] cachefiles: Add some error injection support David Howells
2021-11-29 14:30 ` [PATCH 33/64] cachefiles: Add a couple of tracepoints for logging errors David Howells
2021-11-29 14:31 ` [PATCH 34/64] cachefiles: Add cache error reporting macro David Howells
2021-11-29 14:31 ` David Howells [this message]
2021-11-29 14:31 ` [PATCH 36/64] cachefiles: Register a miscdev and parse commands over it David Howells
2021-11-29 14:31 ` [PATCH 37/64] cachefiles: Provide a function to check how much space there is David Howells
2021-11-29 14:31 ` [PATCH 38/64] vfs, cachefiles: Mark a backing file in use with an inode flag David Howells
2021-11-29 14:31 ` [PATCH 39/64] cachefiles: Implement a function to get/create a directory in the cache David Howells
2021-11-29 14:32 ` [PATCH 40/64] cachefiles: Implement cache registration and withdrawal David Howells
2021-11-29 14:32 ` [PATCH 41/64] cachefiles: Implement volume support David Howells
2021-11-29 14:33 ` [PATCH 42/64] cachefiles: Add tracepoints for calls to the VFS David Howells
2021-11-29 14:33 ` [PATCH 43/64] cachefiles: Implement object lifecycle funcs David Howells
2021-11-29 14:33 ` [PATCH 44/64] cachefiles: Implement key to filename encoding David Howells
2021-12-01  5:46   ` JeffleXu
2021-12-01  8:29   ` David Howells
2021-11-29 14:33 ` [PATCH 45/64] cachefiles: Implement metadata/coherency data storage in xattrs David Howells
2021-11-29 14:33 ` [PATCH 46/64] cachefiles: Mark a backing file in use with an inode flag David Howells
2021-11-29 14:33 ` [PATCH 47/64] cachefiles: Implement culling daemon commands David Howells
2021-11-29 14:34 ` [PATCH 48/64] cachefiles: Implement backing file wrangling David Howells
2021-11-29 14:34 ` [PATCH 49/64] cachefiles: Implement begin and end I/O operation David Howells
2021-11-29 14:34 ` [PATCH 50/64] cachefiles: Implement cookie resize for truncate David Howells
2021-11-29 14:34 ` [PATCH 51/64] cachefiles: Implement the I/O routines David Howells
2021-11-30 16:15   ` Nathan Chancellor
2021-11-30 21:05   ` David Howells
2021-11-29 14:34 ` [PATCH 52/64] cachefiles: Allow cachefiles to actually function David Howells
2021-11-29 14:35 ` [PATCH 53/64] fscache, cachefiles: Display stats of no-space events David Howells
2021-11-29 14:35 ` [PATCH 54/64] fscache, cachefiles: Display stat of culling events David Howells
2021-11-29 14:36 ` [PATCH 55/64] afs: Handle len being extending over page end in write_begin/write_end David Howells
2021-11-29 14:36 ` [PATCH 56/64] afs: Fix afs_write_end() to handle len > page size David Howells
2021-11-29 14:36 ` [PATCH 57/64] afs: Convert afs to use the new fscache API David Howells
2021-11-29 14:37 ` [PATCH 58/64] afs: Copy local writes to the cache when writing to the server David Howells
2021-11-29 14:37 ` [PATCH 59/64] afs: Skip truncation on the server of data we haven't written yet David Howells
2021-11-29 14:37 ` [PATCH 60/64] 9p: Use fscache indexing rewrite and reenable caching David Howells
2021-11-29 14:37 ` [PATCH 61/64] 9p: Copy local writes to the cache when writing to the server David Howells
2021-11-29 14:38 ` [PATCH 62/64] nfs: Convert to new fscache volume/cookie API David Howells
2021-11-29 14:38 ` [PATCH 63/64] cifs: Support fscache indexing rewrite (untested) David Howells
2021-11-29 14:38 ` [PATCH 64/64] fscache: Rewrite documentation David Howells
2021-11-29 18:12 ` [PATCH 00/64] fscache, cachefiles: Rewrite Linus Torvalds
2021-11-29 21:40 ` [PATCH 35/64] cachefiles: Add security derivation David Howells

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