1 files changed, 44 insertions, 3 deletions

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 69a83b59dce8..c614175876e0 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;