1 files changed, 44 insertions, 3 deletions

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 69a83b5..c614175 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -155,6 +155,42 @@ out:
 	return err;
 }
 
+static int check_mode(const struct msdos_sb_info *sbi, mode_t mode)
+{
+	mode_t req = mode & ~S_IFMT;
+
+	/*
+	 * Of the r and x bits, all (subject to umask) must be present. Of the
+	 * w bits, either all (subject to umask) or none must be present.
+	 */
+
+	if (S_ISREG(mode)) {
+		req &= ~sbi->options.fs_fmask;
+
+		if ((req & (S_IRUGO | S_IXUGO)) !=
+		    ((S_IRUGO | S_IXUGO) & ~sbi->options.fs_fmask))
+			return -EPERM;
+
+		if ((req & S_IWUGO) != 0 &&
+		    (req & S_IWUGO) != (S_IWUGO & ~sbi->options.fs_fmask))
+			return -EPERM;
+	} else if (S_ISDIR(mode)) {
+		req &= ~sbi->options.fs_dmask;
+
+		if ((req & (S_IRUGO | S_IXUGO)) !=
+		    ((S_IRUGO | S_IXUGO) & ~sbi->options.fs_dmask))
+			return -EPERM;
+
+		if ((req & S_IWUGO) != 0 &&
+		    (req & S_IWUGO) != (S_IWUGO & ~sbi->options.fs_dmask))
+			return -EPERM;
+	} else {
+		return -EPERM;
+	}
+
+	return 0;
+}
+
 int fat_notify_change(struct dentry *dentry, struct iattr *attr)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
@@ -186,9 +222,7 @@ int fat_notify_change(struct dentry *dentry, struct iattr *attr)
 	if (((attr->ia_valid & ATTR_UID) &&
 	     (attr->ia_uid != sbi->options.fs_uid)) ||
 	    ((attr->ia_valid & ATTR_GID) &&
-	     (attr->ia_gid != sbi->options.fs_gid)) ||
-	    ((attr->ia_valid & ATTR_MODE) &&
-	     (attr->ia_mode & ~MSDOS_VALID_MODE)))
+	     (attr->ia_gid != sbi->options.fs_gid)))
 		error = -EPERM;
 
 	if (error) {
@@ -196,6 +230,13 @@ int fat_notify_change(struct dentry *dentry, struct iattr *attr)
 			error = 0;
 		goto out;
 	}
+
+	if (attr->ia_valid & ATTR_MODE) {
+		error = check_mode(sbi, attr->ia_mode);
+		if (error != 0 && !sbi->options.quiet)
+			goto out;
+	}
+
 	error = inode_setattr(inode, attr);
 	if (error)
 		goto out;