add patch for self-stacking

diff --git a/bug-fixes/andrew-fix-self-stack.log b/bug-fixes/andrew-fix-self-stack.log
new file mode 100644 (file)
index 0000000..69d245f
--- /dev/null
+++ b/bug-fixes/andrew-fix-self-stack.log
@@ -0,0 +1,9 @@
+Wrapfs: fix NULL pointer dereference when stacking wrapfs on top of itself.
+
+Wrapfs assumes that the d_fsdata field has already been initialized whenever
+it is passed one of its own dentries, but it doesn't give the lower fs a chance
+to allocate their d_fsdata field when it creates a new lower_dentry. This is
+fixed by simply replacing a call to d_add in __wrapfs_lookup with a call to
+->lookup on the lower fs inode.
+
+Signed-off-by: Andrew Burford <aburford@cs.stonybrook.edu>

diff --git a/bug-fixes/andrew-fix-self-stack.patch b/bug-fixes/andrew-fix-self-stack.patch
new file mode 100644 (file)
index 0000000..46d3dc5
--- /dev/null
+++ b/bug-fixes/andrew-fix-self-stack.patch
@@ -0,0 +1,20 @@
+diff --git a/fs/wrapfs/lookup.c b/fs/wrapfs/lookup.c
+index 7c78d5a..b166c0e 100644
+--- a/fs/wrapfs/lookup.c
++++ b/fs/wrapfs/lookup.c
+@@ -260,7 +260,14 @@ static struct dentry *__wrapfs_lookup(struct dentry *dentry,
+               err = -ENOMEM;
+               goto out;
+       }
+-      d_add(lower_dentry, NULL); /* instantiate and hash */
++
++      /*
++       * Calling ->lookup instead of d_add will give the lower fs a chance
++       * to allocate the d_fsdata field but will still instantiate and hash the
++       * lower_dentry. Without this, wrapfs could not stack on top of itself.
++       */
++      d_inode(lower_dir_dentry)
++              ->i_op->lookup(d_inode(lower_dir_dentry), lower_dentry, flags);
+ 
+ setup_lower:
+       lower_path.dentry = lower_dentry;