1 files changed, 346 insertions, 0 deletions
diff --git a/fs/attr.c b/fs/attr.c
new file mode 100644
index 000000000..d22e81874
--- /dev/null
+++ b/fs/attr.c
@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/attr.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  changes by Thomas Schoebel-Theuer
+ */
+
+#include <linux/export.h>
+#include <linux/time.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/sched/signal.h>
+#include <linux/capability.h>
+#include <linux/fsnotify.h>
+#include <linux/fcntl.h>
+#include <linux/security.h>
+#include <linux/evm.h>
+#include <linux/ima.h>
+
+static bool chown_ok(const struct inode *inode, kuid_t uid)
+{
+	if (uid_eq(current_fsuid(), inode->i_uid) &&
+	    uid_eq(uid, inode->i_uid))
+		return true;
+	if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))
+		return true;
+	if (uid_eq(inode->i_uid, INVALID_UID) &&
+	    ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
+		return true;
+	return false;
+}
+
+static bool chgrp_ok(const struct inode *inode, kgid_t gid)
+{
+	if (uid_eq(current_fsuid(), inode->i_uid) &&
+	    (in_group_p(gid) || gid_eq(gid, inode->i_gid)))
+		return true;
+	if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))
+		return true;
+	if (gid_eq(inode->i_gid, INVALID_GID) &&
+	    ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
+		return true;
+	return false;
+}
+
+/**
+ * setattr_prepare - check if attribute changes to a dentry are allowed
+ * @dentry:	dentry to check
+ * @attr:	attributes to change
+ *
+ * Check if we are allowed to change the attributes contained in @attr
+ * in the given dentry.  This includes the normal unix access permission
+ * checks, as well as checks for rlimits and others. The function also clears
+ * SGID bit from mode if user is not allowed to set it. Also file capabilities
+ * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
+ *
+ * Should be called as the first thing in ->setattr implementations,
+ * possibly after taking additional locks.
+ */
+int setattr_prepare(struct dentry *dentry, struct iattr *attr)
+{
+	struct inode *inode = d_inode(dentry);
+	unsigned int ia_valid = attr->ia_valid;
+
+	/*
+	 * First check size constraints.  These can't be overriden using
+	 * ATTR_FORCE.
+	 */
+	if (ia_valid & ATTR_SIZE) {
+		int error = inode_newsize_ok(inode, attr->ia_size);
+		if (error)
+			return error;
+	}
+
+	/* If force is set do it anyway. */
+	if (ia_valid & ATTR_FORCE)
+		goto kill_priv;
+
+	/* Make sure a caller can chown. */
+	if ((ia_valid & ATTR_UID) && !chown_ok(inode, attr->ia_uid))
+		return -EPERM;
+
+	/* Make sure caller can chgrp. */
+	if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid))
+		return -EPERM;
+
+	/* Make sure a caller can chmod. */
+	if (ia_valid & ATTR_MODE) {
+		if (!inode_owner_or_capable(inode))
+			return -EPERM;
+		/* Also check the setgid bit! */
+		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
+				inode->i_gid) &&
+		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
+			attr->ia_mode &= ~S_ISGID;
+	}
+
+	/* Check for setting the inode time. */
+	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
+		if (!inode_owner_or_capable(inode))
+			return -EPERM;
+	}
+
+kill_priv:
+	/* User has permission for the change */
+	if (ia_valid & ATTR_KILL_PRIV) {
+		int error;
+
+		error = security_inode_killpriv(dentry);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(setattr_prepare);
+
+/**
+ * inode_newsize_ok - may this inode be truncated to a given size
+ * @inode:	the inode to be truncated
+ * @offset:	the new size to assign to the inode
+ *
+ * inode_newsize_ok must be called with i_mutex held.
+ *
+ * inode_newsize_ok will check filesystem limits and ulimits to check that the
+ * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
+ * when necessary. Caller must not proceed with inode size change if failure is
+ * returned. @inode must be a file (not directory), with appropriate
+ * permissions to allow truncate (inode_newsize_ok does NOT check these
+ * conditions).
+ *
+ * Return: 0 on success, -ve errno on failure
+ */
+int inode_newsize_ok(const struct inode *inode, loff_t offset)
+{
+	if (inode->i_size < offset) {
+		unsigned long limit;
+
+		limit = rlimit(RLIMIT_FSIZE);
+		if (limit != RLIM_INFINITY && offset > limit)
+			goto out_sig;
+		if (offset > inode->i_sb->s_maxbytes)
+			goto out_big;
+	} else {
+		/*
+		 * truncation of in-use swapfiles is disallowed - it would
+		 * cause subsequent swapout to scribble on the now-freed
+		 * blocks.
+		 */
+		if (IS_SWAPFILE(inode))
+			return -ETXTBSY;
+	}
+
+	return 0;
+out_sig:
+	send_sig(SIGXFSZ, current, 0);
+out_big:
+	return -EFBIG;
+}
+EXPORT_SYMBOL(inode_newsize_ok);
+
+/**
+ * setattr_copy - copy simple metadata updates into the generic inode
+ * @inode:	the inode to be updated
+ * @attr:	the new attributes
+ *
+ * setattr_copy must be called with i_mutex held.
+ *
+ * setattr_copy updates the inode's metadata with that specified
+ * in attr. Noticeably missing is inode size update, which is more complex
+ * as it requires pagecache updates.
+ *
+ * The inode is not marked as dirty after this operation. The rationale is
+ * that for "simple" filesystems, the struct inode is the inode storage.
+ * The caller is free to mark the inode dirty afterwards if needed.
+ */
+void setattr_copy(struct inode *inode, const struct iattr *attr)
+{
+	unsigned int ia_valid = attr->ia_valid;
+
+	if (ia_valid & ATTR_UID)
+		inode->i_uid = attr->ia_uid;
+	if (ia_valid & ATTR_GID)
+		inode->i_gid = attr->ia_gid;
+	if (ia_valid & ATTR_ATIME)
+		inode->i_atime = timespec64_trunc(attr->ia_atime,
+						  inode->i_sb->s_time_gran);
+	if (ia_valid & ATTR_MTIME)
+		inode->i_mtime = timespec64_trunc(attr->ia_mtime,
+						  inode->i_sb->s_time_gran);
+	if (ia_valid & ATTR_CTIME)
+		inode->i_ctime = timespec64_trunc(attr->ia_ctime,
+						  inode->i_sb->s_time_gran);
+	if (ia_valid & ATTR_MODE) {
+		umode_t mode = attr->ia_mode;
+
+		if (!in_group_p(inode->i_gid) &&
+		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
+			mode &= ~S_ISGID;
+		inode->i_mode = mode;
+	}
+}
+EXPORT_SYMBOL(setattr_copy);
+
+/**
+ * notify_change - modify attributes of a filesytem object
+ * @dentry:	object affected
+ * @attr:	new attributes
+ * @delegated_inode: returns inode, if the inode is delegated
+ *
+ * The caller must hold the i_mutex on the affected object.
+ *
+ * If notify_change discovers a delegation in need of breaking,
+ * it will return -EWOULDBLOCK and return a reference to the inode in
+ * delegated_inode.  The caller should then break the delegation and
+ * retry.  Because breaking a delegation may take a long time, the
+ * caller should drop the i_mutex before doing so.
+ *
+ * Alternatively, a caller may pass NULL for delegated_inode.  This may
+ * be appropriate for callers that expect the underlying filesystem not
+ * to be NFS exported.  Also, passing NULL is fine for callers holding
+ * the file open for write, as there can be no conflicting delegation in
+ * that case.
+ */
+int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
+{
+	struct inode *inode = dentry->d_inode;
+	umode_t mode = inode->i_mode;
+	int error;
+	struct timespec64 now;
+	unsigned int ia_valid = attr->ia_valid;
+
+	WARN_ON_ONCE(!inode_is_locked(inode));
+
+	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
+		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+			return -EPERM;
+	}
+
+	/*
+	 * If utimes(2) and friends are called with times == NULL (or both
+	 * times are UTIME_NOW), then we need to check for write permission
+	 */
+	if (ia_valid & ATTR_TOUCH) {
+		if (IS_IMMUTABLE(inode))
+			return -EPERM;
+
+		if (!inode_owner_or_capable(inode)) {
+			error = inode_permission(inode, MAY_WRITE);
+			if (error)
+				return error;
+		}
+	}
+
+	if ((ia_valid & ATTR_MODE)) {
+		umode_t amode = attr->ia_mode;
+		/* Flag setting protected by i_mutex */
+		if (is_sxid(amode))
+			inode->i_flags &= ~S_NOSEC;
+	}
+
+	now = current_time(inode);
+
+	attr->ia_ctime = now;
+	if (!(ia_valid & ATTR_ATIME_SET))
+		attr->ia_atime = now;
+	if (!(ia_valid & ATTR_MTIME_SET))
+		attr->ia_mtime = now;
+	if (ia_valid & ATTR_KILL_PRIV) {
+		error = security_inode_need_killpriv(dentry);
+		if (error < 0)
+			return error;
+		if (error == 0)
+			ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
+	}
+
+	/*
+	 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
+	 * that the function has the ability to reinterpret a mode change
+	 * that's due to these bits. This adds an implicit restriction that
+	 * no function will ever call notify_change with both ATTR_MODE and
+	 * ATTR_KILL_S*ID set.
+	 */
+	if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
+	    (ia_valid & ATTR_MODE))
+		BUG();
+
+	if (ia_valid & ATTR_KILL_SUID) {
+		if (mode & S_ISUID) {
+			ia_valid = attr->ia_valid |= ATTR_MODE;
+			attr->ia_mode = (inode->i_mode & ~S_ISUID);
+		}
+	}
+	if (ia_valid & ATTR_KILL_SGID) {
+		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
+			if (!(ia_valid & ATTR_MODE)) {
+				ia_valid = attr->ia_valid |= ATTR_MODE;
+				attr->ia_mode = inode->i_mode;
+			}
+			attr->ia_mode &= ~S_ISGID;
+		}
+	}
+	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
+		return 0;
+
+	/*
+	 * Verify that uid/gid changes are valid in the target
+	 * namespace of the superblock.
+	 */
+	if (ia_valid & ATTR_UID &&
+	    !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
+		return -EOVERFLOW;
+	if (ia_valid & ATTR_GID &&
+	    !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
+		return -EOVERFLOW;
+
+	/* Don't allow modifications of files with invalid uids or
+	 * gids unless those uids & gids are being made valid.
+	 */
+	if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
+		return -EOVERFLOW;
+	if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
+		return -EOVERFLOW;
+
+	error = security_inode_setattr(dentry, attr);
+	if (error)
+		return error;
+	error = try_break_deleg(inode, delegated_inode);
+	if (error)
+		return error;
+
+	if (inode->i_op->setattr)
+		error = inode->i_op->setattr(dentry, attr);
+	else
+		error = simple_setattr(dentry, attr);
+
+	if (!error) {
+		fsnotify_change(dentry, ia_valid);
+		ima_inode_post_setattr(dentry);
+		evm_inode_post_setattr(dentry, ia_valid);
+	}
+
+	return error;
+}
+EXPORT_SYMBOL(notify_change);