Merge tag 'lsm-pr-20230829' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

Pull LSM updates from Paul Moore:

 - Add proper multi-LSM support for xattrs in the
   security_inode_init_security() hook

   Historically the LSM layer has only allowed a single LSM to add an
   xattr to an inode, with IMA/EVM measuring that and adding its own as
   well. As we work towards promoting IMA/EVM to a "proper LSM" instead
   of the special case that it is now, we need to better support the
   case of multiple LSMs each adding xattrs to an inode and after
   several attempts we now appear to have something that is working
   well. It is worth noting that in the process of making this change we
   uncovered a problem with Smack's SMACK64TRANSMUTE xattr which is also
   fixed in this pull request.

 - Additional LSM hook constification

   Two patches to constify parameters to security_capget() and
   security_binder_transfer_file(). While I generally don't make a
   special note of who submitted these patches, these were the work of
   an Outreachy intern, Khadija Kamran, and that makes me happy;
   hopefully it does the same for all of you reading this.

 - LSM hook comment header fixes

   One patch to add a missing hook comment header, one to fix a minor
   typo.

 - Remove an old, unused credential function declaration

   It wasn't clear to me who should pick this up, but it was trivial,
   obviously correct, and arguably the LSM layer has a vested interest
   in credentials so I merged it. Sadly I'm now noticing that despite my
   subject line cleanup I didn't cleanup the "unsued" misspelling, sigh

* tag 'lsm-pr-20230829' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm:
  lsm: constify the 'file' parameter in security_binder_transfer_file()
  lsm: constify the 'target' parameter in security_capget()
  lsm: add comment block for security_sk_classify_flow LSM hook
  security: Fix ret values doc for security_inode_init_security()
  cred: remove unsued extern declaration change_create_files_as()
  evm: Support multiple LSMs providing an xattr
  evm: Align evm_inode_init_security() definition with LSM infrastructure
  smack: Set the SMACK64TRANSMUTE xattr in smack_inode_init_security()
  security: Allow all LSMs to provide xattrs for inode_init_security hook
  lsm: fix typo in security_file_lock() comment header

2 files changed, 41 insertions, 29 deletions

diff --git a/security/smack/smack.h b/security/smack/smack.h
index aa15ff56ed6e..041688e5a77a 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -128,7 +128,7 @@ struct task_smack {
 
 #define	SMK_INODE_INSTANT	0x01	/* inode is instantiated */
 #define	SMK_INODE_TRANSMUTE	0x02	/* directory is transmuting */
-#define	SMK_INODE_CHANGED	0x04	/* smack was transmuted */
+#define	SMK_INODE_CHANGED	0x04	/* smack was transmuted (unused) */
 #define	SMK_INODE_IMPURE	0x08	/* involved in an impure transaction */
 
 /*
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index a8201cf22f20..65130a791f57 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -52,6 +52,15 @@
 #define SMK_RECEIVING	1
 #define SMK_SENDING	2
 
+/*
+ * Smack uses multiple xattrs.
+ * SMACK64 - for access control,
+ * SMACK64TRANSMUTE - label initialization,
+ * Not saved on files - SMACK64IPIN and SMACK64IPOUT,
+ * Must be set explicitly - SMACK64EXEC and SMACK64MMAP
+ */
+#define SMACK_INODE_INIT_XATTRS 2
+
 #ifdef SMACK_IPV6_PORT_LABELING
 static DEFINE_MUTEX(smack_ipv6_lock);
 static LIST_HEAD(smk_ipv6_port_list);
@@ -973,27 +982,23 @@ static int smack_inode_alloc_security(struct inode *inode)
  * @inode: the newly created inode
  * @dir: containing directory object
  * @qstr: unused
- * @name: where to put the attribute name
- * @value: where to put the attribute value
- * @len: where to put the length of the attribute
+ * @xattrs: where to put the attributes
+ * @xattr_count: current number of LSM-provided xattrs (updated)
  *
  * Returns 0 if it all works out, -ENOMEM if there's no memory
  */
 static int smack_inode_init_security(struct inode *inode, struct inode *dir,
-				     const struct qstr *qstr, const char **name,
-				     void **value, size_t *len)
+				     const struct qstr *qstr,
+				     struct xattr *xattrs, int *xattr_count)
 {
 	struct task_smack *tsp = smack_cred(current_cred());
-	struct inode_smack *issp = smack_inode(inode);
 	struct smack_known *skp = smk_of_task(tsp);
 	struct smack_known *isp = smk_of_inode(inode);
 	struct smack_known *dsp = smk_of_inode(dir);
+	struct xattr *xattr = lsm_get_xattr_slot(xattrs, xattr_count);
 	int may;
 
-	if (name)
-		*name = XATTR_SMACK_SUFFIX;
-
-	if (value && len) {
+	if (xattr) {
 		/*
 		 * If equal, transmuting already occurred in
 		 * smack_dentry_create_files_as(). No need to check again.
@@ -1014,6 +1019,8 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 		if ((tsp->smk_task == tsp->smk_transmuted) ||
 		    (may > 0 && ((may & MAY_TRANSMUTE) != 0) &&
 		     smk_inode_transmutable(dir))) {
+			struct xattr *xattr_transmute;
+
 			/*
 			 * The caller of smack_dentry_create_files_as()
 			 * should have overridden the current cred, so the
@@ -1022,14 +1029,26 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 			 */
 			if (tsp->smk_task != tsp->smk_transmuted)
 				isp = dsp;
-			issp->smk_flags |= SMK_INODE_CHANGED;
+			xattr_transmute = lsm_get_xattr_slot(xattrs,
+							     xattr_count);
+			if (xattr_transmute) {
+				xattr_transmute->value = kmemdup(TRANS_TRUE,
+								 TRANS_TRUE_SIZE,
+								 GFP_NOFS);
+				if (!xattr_transmute->value)
+					return -ENOMEM;
+
+				xattr_transmute->value_len = TRANS_TRUE_SIZE;
+				xattr_transmute->name = XATTR_SMACK_TRANSMUTE;
+			}
 		}
 
-		*value = kstrdup(isp->smk_known, GFP_NOFS);
-		if (*value == NULL)
+		xattr->value = kstrdup(isp->smk_known, GFP_NOFS);
+		if (!xattr->value)
 			return -ENOMEM;
 
-		*len = strlen(isp->smk_known);
+		xattr->value_len = strlen(isp->smk_known);
+		xattr->name = XATTR_SMACK_SUFFIX;
 	}
 
 	return 0;
@@ -3568,20 +3587,12 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 			 * If there is a transmute attribute on the
 			 * directory mark the inode.
 			 */
-			if (isp->smk_flags & SMK_INODE_CHANGED) {
-				isp->smk_flags &= ~SMK_INODE_CHANGED;
-				rc = __vfs_setxattr(&nop_mnt_idmap, dp, inode,
-					XATTR_NAME_SMACKTRANSMUTE,
-					TRANS_TRUE, TRANS_TRUE_SIZE,
-					0);
-			} else {
-				rc = __vfs_getxattr(dp, inode,
-					XATTR_NAME_SMACKTRANSMUTE, trattr,
-					TRANS_TRUE_SIZE);
-				if (rc >= 0 && strncmp(trattr, TRANS_TRUE,
-						       TRANS_TRUE_SIZE) != 0)
-					rc = -EINVAL;
-			}
+			rc = __vfs_getxattr(dp, inode,
+					    XATTR_NAME_SMACKTRANSMUTE, trattr,
+					    TRANS_TRUE_SIZE);
+			if (rc >= 0 && strncmp(trattr, TRANS_TRUE,
+					       TRANS_TRUE_SIZE) != 0)
+				rc = -EINVAL;
 			if (rc >= 0)
 				transflag = SMK_INODE_TRANSMUTE;
 		}
@@ -4919,6 +4930,7 @@ struct lsm_blob_sizes smack_blob_sizes __ro_after_init = {
 	.lbs_ipc = sizeof(struct smack_known *),
 	.lbs_msg_msg = sizeof(struct smack_known *),
 	.lbs_superblock = sizeof(struct superblock_smack),
+	.lbs_xattr_count = SMACK_INODE_INIT_XATTRS,
 };
 
 static struct security_hook_list smack_hooks[] __ro_after_init = {