From: aburford <andrew.burford@stonybrook.edu>
Date: Sun, 15 May 2022 00:05:15 +0000 (-0400)
Subject: add patch for self-stacking
X-Git-Url: https://git.fsl.cs.stonybrook.edu/?a=commitdiff_plain;h=d4599fc7b5979e28003b971008d78d140bda97de;p=wrapfs-mgmt.git

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
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
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;