1 files changed, 33 insertions, 34 deletions

diff --git a/fs/namei.c b/fs/namei.c
index a320371899cf..72d4219c93ac 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -271,7 +271,7 @@ static int check_acl(struct inode *inode, int mask)
 		/* no ->get_acl() calls in RCU mode... */
 		if (is_uncached_acl(acl))
 			return -ECHILD;
-	        return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
+	        return posix_acl_permission(inode, acl, mask);
 	}
 
 	acl = get_acl(inode, ACL_TYPE_ACCESS);
@@ -288,37 +288,51 @@ static int check_acl(struct inode *inode, int mask)
 }
 
 /*
- * This does the basic permission checking
+ * This does the basic UNIX permission checking.
+ *
+ * Note that the POSIX ACL check cares about the MAY_NOT_BLOCK bit,
+ * for RCU walking.
  */
 static int acl_permission_check(struct inode *inode, int mask)
 {
 	unsigned int mode = inode->i_mode;
 
-	if (likely(uid_eq(current_fsuid(), inode->i_uid)))
+	/* Are we the owner? If so, ACL's don't matter */
+	if (likely(uid_eq(current_fsuid(), inode->i_uid))) {
+		mask &= 7;
 		mode >>= 6;
-	else {
-		if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
-			int error = check_acl(inode, mask);
-			if (error != -EAGAIN)
-				return error;
-		}
+		return (mask & ~mode) ? -EACCES : 0;
+	}
 
-		if (in_group_p(inode->i_gid))
-			mode >>= 3;
+	/* Do we have ACL's? */
+	if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
+		int error = check_acl(inode, mask);
+		if (error != -EAGAIN)
+			return error;
 	}
 
+	/* Only RWX matters for group/other mode bits */
+	mask &= 7;
+
 	/*
-	 * If the DACs are ok we don't need any capability check.
+	 * Are the group permissions different from
+	 * the other permissions in the bits we care
+	 * about? Need to check group ownership if so.
 	 */
-	if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
-		return 0;
-	return -EACCES;
+	if (mask & (mode ^ (mode >> 3))) {
+		if (in_group_p(inode->i_gid))
+			mode >>= 3;
+	}
+
+	/* Bits in 'mode' clear that we require? */
+	return (mask & ~mode) ? -EACCES : 0;
 }
 
 /**
  * generic_permission -  check for access rights on a Posix-like filesystem
  * @inode:	inode to check access rights for
- * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
+ * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC,
+ *		%MAY_NOT_BLOCK ...)
  *
  * Used to check for read/write/execute permissions on a file.
  * We use "fsuid" for this, letting us set arbitrary permissions
@@ -3505,12 +3519,14 @@ EXPORT_SYMBOL(user_path_create);
 
 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
 {
+	bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV;
 	int error = may_create(dir, dentry);
 
 	if (error)
 		return error;
 
-	if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
+	if ((S_ISCHR(mode) || S_ISBLK(mode)) && !is_whiteout &&
+	    !capable(CAP_MKNOD))
 		return -EPERM;
 
 	if (!dir->i_op->mknod)
@@ -4345,9 +4361,6 @@ static int do_renameat2(int olddfd, const char __user *oldname, int newdfd,
 	    (flags & RENAME_EXCHANGE))
 		return -EINVAL;
 
-	if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
-		return -EPERM;
-
 	if (flags & RENAME_EXCHANGE)
 		target_flags = 0;
 
@@ -4483,20 +4496,6 @@ SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newna
 	return do_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
 }
 
-int vfs_whiteout(struct inode *dir, struct dentry *dentry)
-{
-	int error = may_create(dir, dentry);
-	if (error)
-		return error;
-
-	if (!dir->i_op->mknod)
-		return -EPERM;
-
-	return dir->i_op->mknod(dir, dentry,
-				S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
-}
-EXPORT_SYMBOL(vfs_whiteout);
-
 int readlink_copy(char __user *buffer, int buflen, const char *link)
 {
 	int len = PTR_ERR(link);