1 files changed, 16 insertions, 10 deletions

diff --git a/fs/attr.c b/fs/attr.c
index ae58bd3f875f..966b73e25f82 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -103,12 +103,11 @@ EXPORT_SYMBOL(inode_setattr);
 int notify_change(struct dentry * dentry, struct iattr * attr)
 {
         struct inode *inode = dentry->d_inode;
-        mode_t mode;
+        mode_t mode = inode->i_mode;
         int error;
         struct timespec now;
         unsigned int ia_valid = attr->ia_valid;
 
-        mode = inode->i_mode;
         now = current_fs_time(inode->i_sb);
 
         attr->ia_ctime = now;
@@ -125,18 +124,25 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
                 if (error)
                         return error;
         }
+
+        /*
+         * 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) {
-                attr->ia_valid &= ~ATTR_KILL_SUID;
                 if (mode & S_ISUID) {
-                        if (!(ia_valid & ATTR_MODE)) {
-                                ia_valid = attr->ia_valid |= ATTR_MODE;
-                                attr->ia_mode = inode->i_mode;
-                        }
-                        attr->ia_mode &= ~S_ISUID;
+                        ia_valid = attr->ia_valid |= ATTR_MODE;
+                        attr->ia_mode = (inode->i_mode & ~S_ISUID);
                 }
         }
         if (ia_valid & ATTR_KILL_SGID) {
-                attr->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;
@@ -145,7 +151,7 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
                         attr->ia_mode &= ~S_ISGID;
                 }
         }
-        if (!attr->ia_valid)
+        if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
                 return 0;
 
         if (ia_valid & ATTR_SIZE)