Merge tag 'fs.acl.rework.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping

Pull VFS acl updates from Christian Brauner:
 "This contains the work that builds a dedicated vfs posix acl api.

  The origins of this work trace back to v5.19 but it took quite a while
  to understand the various filesystem specific implementations in
  sufficient detail and also come up with an acceptable solution.

  As we discussed and seen multiple times the current state of how posix
  acls are handled isn't nice and comes with a lot of problems: The
  current way of handling posix acls via the generic xattr api is error
  prone, hard to maintain, and type unsafe for the vfs until we call
  into the filesystem's dedicated get and set inode operations.

  It is already the case that posix acls are special-cased to death all
  the way through the vfs. There are an uncounted number of hacks that
  operate on the uapi posix acl struct instead of the dedicated vfs
  struct posix_acl. And the vfs must be involved in order to interpret
  and fixup posix acls before storing them to the backing store, caching
  them, reporting them to userspace, or for permission checking.

  Currently a range of hacks and duct tape exist to make this work. As
  with most things this is really no ones fault it's just something that
  happened over time. But the code is hard to understand and difficult
  to maintain and one is constantly at risk of introducing bugs and
  regressions when having to touch it.

  Instead of continuing to hack posix acls through the xattr handlers
  this series builds a dedicated posix acl api solely around the get and
  set inode operations.

  Going forward, the vfs_get_acl(), vfs_remove_acl(), and vfs_set_acl()
  helpers must be used in order to interact with posix acls. They
  operate directly on the vfs internal struct posix_acl instead of
  abusing the uapi posix acl struct as we currently do. In the end this
  removes all of the hackiness, makes the codepaths easier to maintain,
  and gets us type safety.

  This series passes the LTP and xfstests suites without any
  regressions. For xfstests the following combinations were tested:
   - xfs
   - ext4
   - btrfs
   - overlayfs
   - overlayfs on top of idmapped mounts
   - orangefs
   - (limited) cifs

  There's more simplifications for posix acls that we can make in the
  future if the basic api has made it.

  A few implementation details:

   - The series makes sure to retain exactly the same security and
     integrity module permission checks. Especially for the integrity
     modules this api is a win because right now they convert the uapi
     posix acl struct passed to them via a void pointer into the vfs
     struct posix_acl format to perform permission checking on the mode.

     There's a new dedicated security hook for setting posix acls which
     passes the vfs struct posix_acl not a void pointer. Basing checking
     on the posix acl stored in the uapi format is really unreliable.
     The vfs currently hacks around directly in the uapi struct storing
     values that frankly the security and integrity modules can't
     correctly interpret as evidenced by bugs we reported and fixed in
     this area. It's not necessarily even their fault it's just that the
     format we provide to them is sub optimal.

   - Some filesystems like 9p and cifs need access to the dentry in
     order to get and set posix acls which is why they either only
     partially or not even at all implement get and set inode
     operations. For example, cifs allows setxattr() and getxattr()
     operations but doesn't allow permission checking based on posix
     acls because it can't implement a get acl inode operation.

     Thus, this patch series updates the set acl inode operation to take
     a dentry instead of an inode argument. However, for the get acl
     inode operation we can't do this as the old get acl method is
     called in e.g., generic_permission() and inode_permission(). These
     helpers in turn are called in various filesystem's permission inode
     operation. So passing a dentry argument to the old get acl inode
     operation would amount to passing a dentry to the permission inode
     operation which we shouldn't and probably can't do.

     So instead of extending the existing inode operation Christoph
     suggested to add a new one. He also requested to ensure that the
     get and set acl inode operation taking a dentry are consistently
     named. So for this version the old get acl operation is renamed to
     ->get_inode_acl() and a new ->get_acl() inode operation taking a
     dentry is added. With this we can give both 9p and cifs get and set
     acl inode operations and in turn remove their complex custom posix
     xattr handlers.

     In the future I hope to get rid of the inode method duplication but
     it isn't like we have never had this situation. Readdir is just one
     example. And frankly, the overall gain in type safety and the more
     pleasant api wise are simply too big of a benefit to not accept
     this duplication for a while.

   - We've done a full audit of every codepaths using variant of the
     current generic xattr api to get and set posix acls and
     surprisingly it isn't that many places. There's of course always a
     chance that we might have missed some and if so I'm sure we'll find
     them soon enough.

     The crucial codepaths to be converted are obviously stacking
     filesystems such as ecryptfs and overlayfs.

     For a list of all callers currently using generic xattr api helpers
     see [2] including comments whether they support posix acls or not.

   - The old vfs generic posix acl infrastructure doesn't obey the
     create and replace semantics promised on the setxattr(2) manpage.
     This patch series doesn't address this. It really is something we
     should revisit later though.

  The patches are roughly organized as follows:

   (1) Change existing set acl inode operation to take a dentry
       argument (Intended to be a non-functional change)

   (2) Rename existing get acl method (Intended to be a non-functional
       change)

   (3) Implement get and set acl inode operations for filesystems that
       couldn't implement one before because of the missing dentry.
       That's mostly 9p and cifs (Intended to be a non-functional
       change)

   (4) Build posix acl api, i.e., add vfs_get_acl(), vfs_remove_acl(),
       and vfs_set_acl() including security and integrity hooks
       (Intended to be a non-functional change)

   (5) Implement get and set acl inode operations for stacking
       filesystems (Intended to be a non-functional change)

   (6) Switch posix acl handling in stacking filesystems to new posix
       acl api now that all filesystems it can stack upon support it.

   (7) Switch vfs to new posix acl api (semantical change)

   (8) Remove all now unused helpers

   (9) Additional regression fixes reported after we merged this into
       linux-next

  Thanks to Seth for a lot of good discussion around this and
  encouragement and input from Christoph"

* tag 'fs.acl.rework.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: (36 commits)
  posix_acl: Fix the type of sentinel in get_acl
  orangefs: fix mode handling
  ovl: call posix_acl_release() after error checking
  evm: remove dead code in evm_inode_set_acl()
  cifs: check whether acl is valid early
  acl: make vfs_posix_acl_to_xattr() static
  acl: remove a slew of now unused helpers
  9p: use stub posix acl handlers
  cifs: use stub posix acl handlers
  ovl: use stub posix acl handlers
  ecryptfs: use stub posix acl handlers
  evm: remove evm_xattr_acl_change()
  xattr: use posix acl api
  ovl: use posix acl api
  ovl: implement set acl method
  ovl: implement get acl method
  ecryptfs: implement set acl method
  ecryptfs: implement get acl method
  ksmbd: use vfs_remove_acl()
  acl: add vfs_remove_acl()
  ...

5 files changed, 225 insertions, 65 deletions

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 23d484e05e6f..e01cfd4ad896 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -8,7 +8,7 @@
  *
  * File: evm_main.c
  *	implements evm_inode_setxattr, evm_inode_post_setxattr,
- *	evm_inode_removexattr, and evm_verifyxattr
+ *	evm_inode_removexattr, evm_verifyxattr, and evm_inode_set_acl.
  */
 
 #define pr_fmt(fmt) "EVM: "fmt
@@ -435,66 +435,6 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
 }
 
 /*
- * evm_xattr_acl_change - check if passed ACL changes the inode mode
- * @mnt_userns: user namespace of the idmapped mount
- * @dentry: pointer to the affected dentry
- * @xattr_name: requested xattr
- * @xattr_value: requested xattr value
- * @xattr_value_len: requested xattr value length
- *
- * Check if passed ACL changes the inode mode, which is protected by EVM.
- *
- * Returns 1 if passed ACL causes inode mode change, 0 otherwise.
- */
-static int evm_xattr_acl_change(struct user_namespace *mnt_userns,
-				struct dentry *dentry, const char *xattr_name,
-				const void *xattr_value, size_t xattr_value_len)
-{
-#ifdef CONFIG_FS_POSIX_ACL
-	umode_t mode;
-	struct posix_acl *acl = NULL, *acl_res;
-	struct inode *inode = d_backing_inode(dentry);
-	int rc;
-
-	/*
-	 * An earlier comment here mentioned that the idmappings for
-	 * ACL_{GROUP,USER} don't matter since EVM is only interested in the
-	 * mode stored as part of POSIX ACLs. Nonetheless, if it must translate
-	 * from the uapi POSIX ACL representation to the VFS internal POSIX ACL
-	 * representation it should do so correctly. There's no guarantee that
-	 * we won't change POSIX ACLs in a way that ACL_{GROUP,USER} matters
-	 * for the mode at some point and it's difficult to keep track of all
-	 * the LSM and integrity modules and what they do to POSIX ACLs.
-	 *
-	 * Frankly, EVM shouldn't try to interpret the uapi struct for POSIX
-	 * ACLs it received. It requires knowledge that only the VFS is
-	 * guaranteed to have.
-	 */
-	acl = vfs_set_acl_prepare(mnt_userns, i_user_ns(inode),
-				  xattr_value, xattr_value_len);
-	if (IS_ERR_OR_NULL(acl))
-		return 1;
-
-	acl_res = acl;
-	/*
-	 * Passing mnt_userns is necessary to correctly determine the GID in
-	 * an idmapped mount, as the GID is used to clear the setgid bit in
-	 * the inode mode.
-	 */
-	rc = posix_acl_update_mode(mnt_userns, inode, &mode, &acl_res);
-
-	posix_acl_release(acl);
-
-	if (rc)
-		return 1;
-
-	if (inode->i_mode != mode)
-		return 1;
-#endif
-	return 0;
-}
-
-/*
  * evm_xattr_change - check if passed xattr value differs from current value
  * @mnt_userns: user namespace of the idmapped mount
  * @dentry: pointer to the affected dentry
@@ -513,10 +453,6 @@ static int evm_xattr_change(struct user_namespace *mnt_userns,
 	char *xattr_data = NULL;
 	int rc = 0;
 
-	if (posix_xattr_acl(xattr_name))
-		return evm_xattr_acl_change(mnt_userns, dentry, xattr_name,
-					    xattr_value, xattr_value_len);
-
 	rc = vfs_getxattr_alloc(&init_user_ns, dentry, xattr_name, &xattr_data,
 				0, GFP_NOFS);
 	if (rc < 0)
@@ -670,6 +606,86 @@ int evm_inode_removexattr(struct user_namespace *mnt_userns,
 	return evm_protect_xattr(mnt_userns, dentry, xattr_name, NULL, 0);
 }
 
+#ifdef CONFIG_FS_POSIX_ACL
+static int evm_inode_set_acl_change(struct user_namespace *mnt_userns,
+				    struct dentry *dentry, const char *name,
+				    struct posix_acl *kacl)
+{
+	int rc;
+
+	umode_t mode;
+	struct inode *inode = d_backing_inode(dentry);
+
+	if (!kacl)
+		return 1;
+
+	rc = posix_acl_update_mode(mnt_userns, inode, &mode, &kacl);
+	if (rc || (inode->i_mode != mode))
+		return 1;
+
+	return 0;
+}
+#else
+static inline int evm_inode_set_acl_change(struct user_namespace *mnt_userns,
+					   struct dentry *dentry,
+					   const char *name,
+					   struct posix_acl *kacl)
+{
+	return 0;
+}
+#endif
+
+/**
+ * evm_inode_set_acl - protect the EVM extended attribute from posix acls
+ * @mnt_userns: user namespace of the idmapped mount
+ * @dentry: pointer to the affected dentry
+ * @acl_name: name of the posix acl
+ * @kacl: pointer to the posix acls
+ *
+ * Prevent modifying posix acls causing the EVM HMAC to be re-calculated
+ * and 'security.evm' xattr updated, unless the existing 'security.evm' is
+ * valid.
+ */
+int evm_inode_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+		      const char *acl_name, struct posix_acl *kacl)
+{
+	enum integrity_status evm_status;
+
+	/* Policy permits modification of the protected xattrs even though
+	 * there's no HMAC key loaded
+	 */
+	if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
+		return 0;
+
+	evm_status = evm_verify_current_integrity(dentry);
+	if ((evm_status == INTEGRITY_PASS) ||
+	    (evm_status == INTEGRITY_NOXATTRS))
+		return 0;
+
+	/* Exception if the HMAC is not going to be calculated. */
+	if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
+	    evm_status == INTEGRITY_UNKNOWN))
+		return 0;
+
+	/*
+	 * Writing other xattrs is safe for portable signatures, as portable
+	 * signatures are immutable and can never be updated.
+	 */
+	if (evm_status == INTEGRITY_FAIL_IMMUTABLE)
+		return 0;
+
+	if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
+	    !evm_inode_set_acl_change(mnt_userns, dentry, acl_name, kacl))
+		return 0;
+
+	if (evm_status != INTEGRITY_PASS_IMMUTABLE)
+		integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
+				    dentry->d_name.name, "appraise_metadata",
+				    integrity_status_msg[evm_status],
+				    -EPERM, 0);
+	return -EPERM;
+}
+
 static void evm_reset_status(struct inode *inode)
 {
 	struct integrity_iint_cache *iint;
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 3e0fbbd99534..3c9af3dc0713 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -774,6 +774,15 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 	return result;
 }
 
+int ima_inode_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+		      const char *acl_name, struct posix_acl *kacl)
+{
+	if (evm_revalidate_status(acl_name))
+		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
+
+	return 0;
+}
+
 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
 {
 	int result;
diff --git a/security/security.c b/security/security.c
index 79d82cb6e469..bdc295ad5fba 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1372,6 +1372,48 @@ int security_inode_setxattr(struct user_namespace *mnt_userns,
 	return evm_inode_setxattr(mnt_userns, dentry, name, value, size);
 }
 
+int security_inode_set_acl(struct user_namespace *mnt_userns,
+			   struct dentry *dentry, const char *acl_name,
+			   struct posix_acl *kacl)
+{
+	int ret;
+
+	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
+		return 0;
+	ret = call_int_hook(inode_set_acl, 0, mnt_userns, dentry, acl_name,
+			    kacl);
+	if (ret)
+		return ret;
+	ret = ima_inode_set_acl(mnt_userns, dentry, acl_name, kacl);
+	if (ret)
+		return ret;
+	return evm_inode_set_acl(mnt_userns, dentry, acl_name, kacl);
+}
+
+int security_inode_get_acl(struct user_namespace *mnt_userns,
+			   struct dentry *dentry, const char *acl_name)
+{
+	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
+		return 0;
+	return call_int_hook(inode_get_acl, 0, mnt_userns, dentry, acl_name);
+}
+
+int security_inode_remove_acl(struct user_namespace *mnt_userns,
+			      struct dentry *dentry, const char *acl_name)
+{
+	int ret;
+
+	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
+		return 0;
+	ret = call_int_hook(inode_remove_acl, 0, mnt_userns, dentry, acl_name);
+	if (ret)
+		return ret;
+	ret = ima_inode_remove_acl(mnt_userns, dentry, acl_name);
+	if (ret)
+		return ret;
+	return evm_inode_remove_acl(mnt_userns, dentry, acl_name);
+}
+
 void security_inode_post_setxattr(struct dentry *dentry, const char *name,
 				  const void *value, size_t size, int flags)
 {
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index f553c370397e..7c5c8d17695c 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3240,6 +3240,25 @@ static int selinux_inode_setxattr(struct user_namespace *mnt_userns,
 			    &ad);
 }
 
+static int selinux_inode_set_acl(struct user_namespace *mnt_userns,
+				 struct dentry *dentry, const char *acl_name,
+				 struct posix_acl *kacl)
+{
+	return dentry_has_perm(current_cred(), dentry, FILE__SETATTR);
+}
+
+static int selinux_inode_get_acl(struct user_namespace *mnt_userns,
+				 struct dentry *dentry, const char *acl_name)
+{
+	return dentry_has_perm(current_cred(), dentry, FILE__GETATTR);
+}
+
+static int selinux_inode_remove_acl(struct user_namespace *mnt_userns,
+				    struct dentry *dentry, const char *acl_name)
+{
+	return dentry_has_perm(current_cred(), dentry, FILE__SETATTR);
+}
+
 static void selinux_inode_post_setxattr(struct dentry *dentry, const char *name,
 					const void *value, size_t size,
 					int flags)
@@ -7088,6 +7107,9 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(inode_getxattr, selinux_inode_getxattr),
 	LSM_HOOK_INIT(inode_listxattr, selinux_inode_listxattr),
 	LSM_HOOK_INIT(inode_removexattr, selinux_inode_removexattr),
+	LSM_HOOK_INIT(inode_set_acl, selinux_inode_set_acl),
+	LSM_HOOK_INIT(inode_get_acl, selinux_inode_get_acl),
+	LSM_HOOK_INIT(inode_remove_acl, selinux_inode_remove_acl),
 	LSM_HOOK_INIT(inode_getsecurity, selinux_inode_getsecurity),
 	LSM_HOOK_INIT(inode_setsecurity, selinux_inode_setsecurity),
 	LSM_HOOK_INIT(inode_listsecurity, selinux_inode_listsecurity),
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index b6306d71c908..cadef2f6a75e 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1393,6 +1393,74 @@ static int smack_inode_removexattr(struct user_namespace *mnt_userns,
 }
 
 /**
+ * smack_inode_set_acl - Smack check for setting posix acls
+ * @mnt_userns: the userns attached to the mnt this request came from
+ * @dentry: the object
+ * @acl_name: name of the posix acl
+ * @kacl: the posix acls
+ *
+ * Returns 0 if access is permitted, an error code otherwise
+ */
+static int smack_inode_set_acl(struct user_namespace *mnt_userns,
+			       struct dentry *dentry, const char *acl_name,
+			       struct posix_acl *kacl)
+{
+	struct smk_audit_info ad;
+	int rc;
+
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_DENTRY);
+	smk_ad_setfield_u_fs_path_dentry(&ad, dentry);
+
+	rc = smk_curacc(smk_of_inode(d_backing_inode(dentry)), MAY_WRITE, &ad);
+	rc = smk_bu_inode(d_backing_inode(dentry), MAY_WRITE, rc);
+	return rc;
+}
+
+/**
+ * smack_inode_get_acl - Smack check for getting posix acls
+ * @mnt_userns: the userns attached to the mnt this request came from
+ * @dentry: the object
+ * @acl_name: name of the posix acl
+ *
+ * Returns 0 if access is permitted, an error code otherwise
+ */
+static int smack_inode_get_acl(struct user_namespace *mnt_userns,
+			       struct dentry *dentry, const char *acl_name)
+{
+	struct smk_audit_info ad;
+	int rc;
+
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_DENTRY);
+	smk_ad_setfield_u_fs_path_dentry(&ad, dentry);
+
+	rc = smk_curacc(smk_of_inode(d_backing_inode(dentry)), MAY_READ, &ad);
+	rc = smk_bu_inode(d_backing_inode(dentry), MAY_READ, rc);
+	return rc;
+}
+
+/**
+ * smack_inode_remove_acl - Smack check for getting posix acls
+ * @mnt_userns: the userns attached to the mnt this request came from
+ * @dentry: the object
+ * @acl_name: name of the posix acl
+ *
+ * Returns 0 if access is permitted, an error code otherwise
+ */
+static int smack_inode_remove_acl(struct user_namespace *mnt_userns,
+				  struct dentry *dentry, const char *acl_name)
+{
+	struct smk_audit_info ad;
+	int rc;
+
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_DENTRY);
+	smk_ad_setfield_u_fs_path_dentry(&ad, dentry);
+
+	rc = smk_curacc(smk_of_inode(d_backing_inode(dentry)), MAY_WRITE, &ad);
+	rc = smk_bu_inode(d_backing_inode(dentry), MAY_WRITE, rc);
+	return rc;
+}
+
+/**
  * smack_inode_getsecurity - get smack xattrs
  * @mnt_userns: active user namespace
  * @inode: the object
@@ -4816,6 +4884,9 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(inode_post_setxattr, smack_inode_post_setxattr),
 	LSM_HOOK_INIT(inode_getxattr, smack_inode_getxattr),
 	LSM_HOOK_INIT(inode_removexattr, smack_inode_removexattr),
+	LSM_HOOK_INIT(inode_set_acl, smack_inode_set_acl),
+	LSM_HOOK_INIT(inode_get_acl, smack_inode_get_acl),
+	LSM_HOOK_INIT(inode_remove_acl, smack_inode_remove_acl),
 	LSM_HOOK_INIT(inode_getsecurity, smack_inode_getsecurity),
 	LSM_HOOK_INIT(inode_setsecurity, smack_inode_setsecurity),
 	LSM_HOOK_INIT(inode_listsecurity, smack_inode_listsecurity),