check ATTR_SIZE contraints in inode_change_ok

Make sure we check the truncate constraints early on in ->setattr by adding
those checks to inode_change_ok.  Also clean up and document inode_change_ok
to make this obvious.

As a fallout we don't have to call inode_newsize_ok from simple_setsize and
simplify it down to a truncate_setsize which doesn't return an error.  This
simplifies a lot of setattr implementations and means we use truncate_setsize
almost everywhere.  Get rid of fat_setsize now that it's trivial and mark
ext2_setsize static to make the calling convention obvious.

Keep the inode_newsize_ok in vmtruncate for now as all callers need an
audit for its removal anyway.

Note: setattr code in ecryptfs doesn't call inode_change_ok at all and
needs a deeper audit, but that is left for later.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 30 insertions, 14 deletions

diff --git a/fs/attr.c b/fs/attr.c
index ed44d8ae8bf1..7ca41811afa1 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -14,35 +14,53 @@
 #include <linux/fcntl.h>
 #include <linux/security.h>
 
-/* Taken over from the old code... */
-
-/* POSIX UID/GID verification for setting inode attributes. */
+/**
+ * inode_change_ok - check if attribute changes to an inode are allowed
+ * @inode:      inode to check
+ * @attr:       attributes to change
+ *
+ * Check if we are allowed to change the attributes contained in @attr
+ * in the given inode.  This includes the normal unix access permission
+ * checks, as well as checks for rlimits and others.
+ *
+ * Should be called as the first thing in ->setattr implementations,
+ * possibly after taking additional locks.
+ */
 int inode_change_ok(const struct inode *inode, struct iattr *attr)
 {
-        int retval = -EPERM;
         unsigned int ia_valid = attr->ia_valid;
 
+        /*
+         * First check size constraints.  These can't be overriden using
+         * ATTR_FORCE.
+         */
+        if (ia_valid & ATTR_SIZE) {
+                int error = inode_newsize_ok(inode, attr->ia_size);
+                if (error)
+                        return error;
+        }
+
         /* If force is set do it anyway. */
         if (ia_valid & ATTR_FORCE)
-                goto fine;
+                return 0;
 
         /* Make sure a caller can chown. */
         if ((ia_valid & ATTR_UID) &&
             (current_fsuid() != inode->i_uid ||
              attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
-                goto error;
+                return -EPERM;
 
         /* Make sure caller can chgrp. */
         if ((ia_valid & ATTR_GID) &&
             (current_fsuid() != inode->i_uid ||
             (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
             !capable(CAP_CHOWN))
-                goto error;
+                return -EPERM;
 
         /* Make sure a caller can chmod. */
         if (ia_valid & ATTR_MODE) {
                 if (!is_owner_or_cap(inode))
-                        goto error;
+                        return -EPERM;
                 /* Also check the setgid bit! */
                 if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
                                 inode->i_gid) && !capable(CAP_FSETID))
@@ -52,12 +70,10 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
         /* Check for setting the inode time. */
         if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
                 if (!is_owner_or_cap(inode))
-                        goto error;
+                        return -EPERM;
         }
-fine:
-        retval = 0;
-error:
-        return retval;
+
+        return 0;
 }
 EXPORT_SYMBOL(inode_change_ok);
 
@@ -113,7 +129,7 @@ EXPORT_SYMBOL(inode_newsize_ok);
  *
  * setattr_copy updates the inode's metadata with that specified
  * in attr. Noticably missing is inode size update, which is more complex
- * as it requires pagecache updates. See simple_setsize.
+ * as it requires pagecache updates.
  *
  * The inode is not marked as dirty after this operation. The rationale is
  * that for "simple" filesystems, the struct inode is the inode storage.