fs: reflow may_create_in_sticky()

This function is so messy and hard to read, let's reflow it to make it
more readable.

Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240621-affekt-denkzettel-3c115f68355a@brauner
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 35 insertions, 16 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 8b40991cb59e..f10b6dde7dab 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1240,29 +1240,48 @@ int may_linkat(struct mnt_idmap *idmap, const struct path *link)
  *
  * Returns 0 if the open is allowed, -ve on error.
  */
-static int may_create_in_sticky(struct mnt_idmap *idmap,
-				struct nameidata *nd, struct inode *const inode)
+static int may_create_in_sticky(struct mnt_idmap *idmap, struct nameidata *nd,
+				struct inode *const inode)
 {
 	umode_t dir_mode = nd->dir_mode;
-	vfsuid_t dir_vfsuid = nd->dir_vfsuid;
+	vfsuid_t dir_vfsuid = nd->dir_vfsuid, i_vfsuid;
 
-	if (likely(!(dir_mode & S_ISVTX)) ||
-	    (S_ISREG(inode->i_mode) && !sysctl_protected_regular) ||
-	    (S_ISFIFO(inode->i_mode) && !sysctl_protected_fifos) ||
-	    vfsuid_eq(i_uid_into_vfsuid(idmap, inode), dir_vfsuid) ||
-	    vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
+	if (likely(!(dir_mode & S_ISVTX)))
 		return 0;
 
-	if (likely(dir_mode & 0002) ||
-	    (dir_mode & 0020 &&
-	     ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
-	      (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
-		const char *operation = S_ISFIFO(inode->i_mode) ?
-					"sticky_create_fifo" :
-					"sticky_create_regular";
-		audit_log_path_denied(AUDIT_ANOM_CREAT, operation);
+	if (S_ISREG(inode->i_mode) && !sysctl_protected_regular)
+		return 0;
+
+	if (S_ISFIFO(inode->i_mode) && !sysctl_protected_fifos)
+		return 0;
+
+	i_vfsuid = i_uid_into_vfsuid(idmap, inode);
+
+	if (vfsuid_eq(i_vfsuid, dir_vfsuid))
+		return 0;
+
+	if (vfsuid_eq_kuid(i_vfsuid, current_fsuid()))
+		return 0;
+
+	if (likely(dir_mode & 0002)) {
+		audit_log_path_denied(AUDIT_ANOM_CREAT, "sticky_create");
 		return -EACCES;
 	}
+
+	if (dir_mode & 0020) {
+		if (sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) {
+			audit_log_path_denied(AUDIT_ANOM_CREAT,
+					      "sticky_create_fifo");
+			return -EACCES;
+		}
+
+		if (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode)) {
+			audit_log_path_denied(AUDIT_ANOM_CREAT,
+					      "sticky_create_regular");
+			return -EACCES;
+		}
+	}
+
 	return 0;
 }