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, 170 insertions, 146 deletions

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 4dac4a0dc5f4..c397c51f80d9 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -17,34 +17,64 @@
 #include "v9fs_vfs.h"
 #include "fid.h"
 
-static struct posix_acl *__v9fs_get_acl(struct p9_fid *fid, char *name)
+static struct posix_acl *v9fs_fid_get_acl(struct p9_fid *fid, const char *name)
 {
 	ssize_t size;
 	void *value = NULL;
 	struct posix_acl *acl = NULL;
 
 	size = v9fs_fid_xattr_get(fid, name, NULL, 0);
-	if (size > 0) {
-		value = kzalloc(size, GFP_NOFS);
-		if (!value)
-			return ERR_PTR(-ENOMEM);
-		size = v9fs_fid_xattr_get(fid, name, value, size);
-		if (size > 0) {
-			acl = posix_acl_from_xattr(&init_user_ns, value, size);
-			if (IS_ERR(acl))
-				goto err_out;
-		}
-	} else if (size == -ENODATA || size == 0 ||
-		   size == -ENOSYS || size == -EOPNOTSUPP) {
-		acl = NULL;
-	} else
-		acl = ERR_PTR(-EIO);
-
-err_out:
+	if (size < 0)
+		return ERR_PTR(size);
+	if (size == 0)
+		return ERR_PTR(-ENODATA);
+
+	value = kzalloc(size, GFP_NOFS);
+	if (!value)
+		return ERR_PTR(-ENOMEM);
+
+	size = v9fs_fid_xattr_get(fid, name, value, size);
+	if (size < 0)
+		acl = ERR_PTR(size);
+	else if (size == 0)
+		acl = ERR_PTR(-ENODATA);
+	else
+		acl = posix_acl_from_xattr(&init_user_ns, value, size);
 	kfree(value);
 	return acl;
 }
 
+static struct posix_acl *v9fs_acl_get(struct dentry *dentry, const char *name)
+{
+	struct p9_fid *fid;
+	struct posix_acl *acl = NULL;
+
+	fid = v9fs_fid_lookup(dentry);
+	if (IS_ERR(fid))
+		return ERR_CAST(fid);
+
+	acl = v9fs_fid_get_acl(fid, name);
+	p9_fid_put(fid);
+	return acl;
+}
+
+static struct posix_acl *__v9fs_get_acl(struct p9_fid *fid, const char *name)
+{
+	int retval;
+	struct posix_acl *acl = NULL;
+
+	acl = v9fs_fid_get_acl(fid, name);
+	if (!IS_ERR(acl))
+		return acl;
+
+	retval = PTR_ERR(acl);
+	if (retval == -ENODATA || retval == -ENOSYS || retval == -EOPNOTSUPP)
+		return NULL;
+
+	/* map everything else to -EIO */
+	return ERR_PTR(-EIO);
+}
+
 int v9fs_get_acl(struct inode *inode, struct p9_fid *fid)
 {
 	int retval = 0;
@@ -89,7 +119,7 @@ static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
 	return acl;
 }
 
-struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type, bool rcu)
+struct posix_acl *v9fs_iop_get_inode_acl(struct inode *inode, int type, bool rcu)
 {
 	struct v9fs_session_info *v9ses;
 
@@ -109,6 +139,112 @@ struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type, bool rcu)
 
 }
 
+struct posix_acl *v9fs_iop_get_acl(struct user_namespace *mnt_userns,
+				   struct dentry *dentry, int type)
+{
+	struct v9fs_session_info *v9ses;
+
+	v9ses = v9fs_dentry2v9ses(dentry);
+	/* We allow set/get/list of acl when access=client is not specified. */
+	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT)
+		return v9fs_acl_get(dentry, posix_acl_xattr_name(type));
+	return v9fs_get_cached_acl(d_inode(dentry), type);
+}
+
+int v9fs_iop_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+		     struct posix_acl *acl, int type)
+{
+	int retval;
+	size_t size = 0;
+	void *value = NULL;
+	const char *acl_name;
+	struct v9fs_session_info *v9ses;
+	struct inode *inode = d_inode(dentry);
+
+	if (acl) {
+		retval = posix_acl_valid(inode->i_sb->s_user_ns, acl);
+		if (retval)
+			goto err_out;
+
+		size = posix_acl_xattr_size(acl->a_count);
+
+		value = kzalloc(size, GFP_NOFS);
+		if (!value) {
+			retval = -ENOMEM;
+			goto err_out;
+		}
+
+		retval = posix_acl_to_xattr(&init_user_ns, acl, value, size);
+		if (retval < 0)
+			goto err_out;
+	}
+
+	/*
+	 * set the attribute on the remote. Without even looking at the
+	 * xattr value. We leave it to the server to validate
+	 */
+	acl_name = posix_acl_xattr_name(type);
+	v9ses = v9fs_dentry2v9ses(dentry);
+	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT) {
+		retval = v9fs_xattr_set(dentry, acl_name, value, size, 0);
+		goto err_out;
+	}
+
+	if (S_ISLNK(inode->i_mode)) {
+		retval = -EOPNOTSUPP;
+		goto err_out;
+	}
+
+	if (!inode_owner_or_capable(&init_user_ns, inode)) {
+		retval = -EPERM;
+		goto err_out;
+	}
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		if (acl) {
+			struct iattr iattr = {};
+			struct posix_acl *acl_mode = acl;
+
+			retval = posix_acl_update_mode(&init_user_ns, inode,
+						       &iattr.ia_mode,
+						       &acl_mode);
+			if (retval)
+				goto err_out;
+			if (!acl_mode) {
+				/*
+				 * ACL can be represented by the mode bits.
+				 * So don't update ACL below.
+				 */
+				kfree(value);
+				value = NULL;
+				size = 0;
+			}
+			iattr.ia_valid = ATTR_MODE;
+			/*
+			 * FIXME should we update ctime ?
+			 * What is the following setxattr update the mode ?
+			 */
+			v9fs_vfs_setattr_dotl(&init_user_ns, dentry, &iattr);
+		}
+		break;
+	case ACL_TYPE_DEFAULT:
+		if (!S_ISDIR(inode->i_mode)) {
+			retval = acl ? -EINVAL : 0;
+			goto err_out;
+		}
+		break;
+	}
+
+	retval = v9fs_xattr_set(dentry, acl_name, value, size, 0);
+	if (!retval)
+		set_cached_acl(inode, type, acl);
+
+err_out:
+	kfree(value);
+	return retval;
+}
+
 static int v9fs_set_acl(struct p9_fid *fid, int type, struct posix_acl *acl)
 {
 	int retval;
@@ -207,124 +343,3 @@ int v9fs_acl_mode(struct inode *dir, umode_t *modep,
 	*modep  = mode;
 	return 0;
 }
-
-static int v9fs_xattr_get_acl(const struct xattr_handler *handler,
-			      struct dentry *dentry, struct inode *inode,
-			      const char *name, void *buffer, size_t size)
-{
-	struct v9fs_session_info *v9ses;
-	struct posix_acl *acl;
-	int error;
-
-	v9ses = v9fs_dentry2v9ses(dentry);
-	/*
-	 * We allow set/get/list of acl when access=client is not specified
-	 */
-	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT)
-		return v9fs_xattr_get(dentry, handler->name, buffer, size);
-
-	acl = v9fs_get_cached_acl(inode, handler->flags);
-	if (IS_ERR(acl))
-		return PTR_ERR(acl);
-	if (acl == NULL)
-		return -ENODATA;
-	error = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
-	posix_acl_release(acl);
-
-	return error;
-}
-
-static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
-			      struct user_namespace *mnt_userns,
-			      struct dentry *dentry, struct inode *inode,
-			      const char *name, const void *value,
-			      size_t size, int flags)
-{
-	int retval;
-	struct posix_acl *acl;
-	struct v9fs_session_info *v9ses;
-
-	v9ses = v9fs_dentry2v9ses(dentry);
-	/*
-	 * set the attribute on the remote. Without even looking at the
-	 * xattr value. We leave it to the server to validate
-	 */
-	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT)
-		return v9fs_xattr_set(dentry, handler->name, value, size,
-				      flags);
-
-	if (S_ISLNK(inode->i_mode))
-		return -EOPNOTSUPP;
-	if (!inode_owner_or_capable(&init_user_ns, inode))
-		return -EPERM;
-	if (value) {
-		/* update the cached acl value */
-		acl = posix_acl_from_xattr(&init_user_ns, value, size);
-		if (IS_ERR(acl))
-			return PTR_ERR(acl);
-		else if (acl) {
-			retval = posix_acl_valid(inode->i_sb->s_user_ns, acl);
-			if (retval)
-				goto err_out;
-		}
-	} else
-		acl = NULL;
-
-	switch (handler->flags) {
-	case ACL_TYPE_ACCESS:
-		if (acl) {
-			struct iattr iattr = { 0 };
-			struct posix_acl *old_acl = acl;
-
-			retval = posix_acl_update_mode(&init_user_ns, inode,
-						       &iattr.ia_mode, &acl);
-			if (retval)
-				goto err_out;
-			if (!acl) {
-				/*
-				 * ACL can be represented
-				 * by the mode bits. So don't
-				 * update ACL.
-				 */
-				posix_acl_release(old_acl);
-				value = NULL;
-				size = 0;
-			}
-			iattr.ia_valid = ATTR_MODE;
-			/* FIXME should we update ctime ?
-			 * What is the following setxattr update the
-			 * mode ?
-			 */
-			v9fs_vfs_setattr_dotl(&init_user_ns, dentry, &iattr);
-		}
-		break;
-	case ACL_TYPE_DEFAULT:
-		if (!S_ISDIR(inode->i_mode)) {
-			retval = acl ? -EINVAL : 0;
-			goto err_out;
-		}
-		break;
-	default:
-		BUG();
-	}
-	retval = v9fs_xattr_set(dentry, handler->name, value, size, flags);
-	if (!retval)
-		set_cached_acl(inode, handler->flags, acl);
-err_out:
-	posix_acl_release(acl);
-	return retval;
-}
-
-const struct xattr_handler v9fs_xattr_acl_access_handler = {
-	.name	= XATTR_NAME_POSIX_ACL_ACCESS,
-	.flags	= ACL_TYPE_ACCESS,
-	.get	= v9fs_xattr_get_acl,
-	.set	= v9fs_xattr_set_acl,
-};
-
-const struct xattr_handler v9fs_xattr_acl_default_handler = {
-	.name	= XATTR_NAME_POSIX_ACL_DEFAULT,
-	.flags	= ACL_TYPE_DEFAULT,
-	.get	= v9fs_xattr_get_acl,
-	.set	= v9fs_xattr_set_acl,
-};
diff --git a/fs/9p/acl.h b/fs/9p/acl.h
index ce5175d463dd..4c60a2bce5de 100644
--- a/fs/9p/acl.h
+++ b/fs/9p/acl.h
@@ -8,8 +8,12 @@
 
 #ifdef CONFIG_9P_FS_POSIX_ACL
 int v9fs_get_acl(struct inode *inode, struct p9_fid *fid);
-struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type,
+struct posix_acl *v9fs_iop_get_inode_acl(struct inode *inode, int type,
 				   bool rcu);
+struct posix_acl *v9fs_iop_get_acl(struct user_namespace *mnt_userns,
+					  struct dentry *dentry, int type);
+int v9fs_iop_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+		     struct posix_acl *acl, int type);
 int v9fs_acl_chmod(struct inode *inode, struct p9_fid *fid);
 int v9fs_set_create_acl(struct inode *inode, struct p9_fid *fid,
 			struct posix_acl *dacl, struct posix_acl *acl);
@@ -17,7 +21,9 @@ int v9fs_acl_mode(struct inode *dir, umode_t *modep,
 		  struct posix_acl **dpacl, struct posix_acl **pacl);
 void v9fs_put_acl(struct posix_acl *dacl, struct posix_acl *acl);
 #else
+#define v9fs_iop_get_inode_acl	NULL
 #define v9fs_iop_get_acl NULL
+#define v9fs_iop_set_acl NULL
 static inline int v9fs_get_acl(struct inode *inode, struct p9_fid *fid)
 {
 	return 0;
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 5cfa4b4f070f..03c1743c4aff 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -983,14 +983,18 @@ const struct inode_operations v9fs_dir_inode_operations_dotl = {
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,
 	.listxattr = v9fs_listxattr,
+	.get_inode_acl = v9fs_iop_get_inode_acl,
 	.get_acl = v9fs_iop_get_acl,
+	.set_acl = v9fs_iop_set_acl,
 };
 
 const struct inode_operations v9fs_file_inode_operations_dotl = {
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,
 	.listxattr = v9fs_listxattr,
+	.get_inode_acl = v9fs_iop_get_inode_acl,
 	.get_acl = v9fs_iop_get_acl,
+	.set_acl = v9fs_iop_set_acl,
 };
 
 const struct inode_operations v9fs_symlink_inode_operations_dotl = {
diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index 2807bb63f780..b6984311e00a 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -8,6 +8,7 @@
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/uio.h>
+#include <linux/posix_acl_xattr.h>
 #include <net/9p/9p.h>
 #include <net/9p/client.h>
 
@@ -182,9 +183,9 @@ static struct xattr_handler v9fs_xattr_security_handler = {
 const struct xattr_handler *v9fs_xattr_handlers[] = {
 	&v9fs_xattr_user_handler,
 	&v9fs_xattr_trusted_handler,
-#ifdef CONFIG_9P_FS_POSIX_ACL
-	&v9fs_xattr_acl_access_handler,
-	&v9fs_xattr_acl_default_handler,
+#ifdef CONFIG_FS_POSIX_ACL
+	&posix_acl_access_xattr_handler,
+	&posix_acl_default_xattr_handler,
 #endif
 #ifdef CONFIG_9P_FS_SECURITY
 	&v9fs_xattr_security_handler,
diff --git a/fs/9p/xattr.h b/fs/9p/xattr.h
index 3e11fc3331eb..b5636e544c8a 100644
--- a/fs/9p/xattr.h
+++ b/fs/9p/xattr.h
@@ -11,8 +11,6 @@
 #include <net/9p/client.h>
 
 extern const struct xattr_handler *v9fs_xattr_handlers[];
-extern const struct xattr_handler v9fs_xattr_acl_access_handler;
-extern const struct xattr_handler v9fs_xattr_acl_default_handler;
 
 ssize_t v9fs_fid_xattr_get(struct p9_fid *fid, const char *name,
 			   void *buffer, size_t buffer_size);