netfs: Fix gcc-12 warning by embedding vfs inode in netfs_i_context

While randstruct was satisfied with using an open-coded "void *" offset
cast for the netfs_i_context <-> inode casting, __builtin_object_size() as
used by FORTIFY_SOURCE was not as easily fooled.  This was causing the
following complaint[1] from gcc v12:

  In file included from include/linux/string.h:253,
                   from include/linux/ceph/ceph_debug.h:7,
                   from fs/ceph/inode.c:2:
  In function 'fortify_memset_chk',
      inlined from 'netfs_i_context_init' at include/linux/netfs.h:326:2,
      inlined from 'ceph_alloc_inode' at fs/ceph/inode.c:463:2:
  include/linux/fortify-string.h:242:25: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
    242 |                         __write_overflow_field(p_size_field, size);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by embedding a struct inode into struct netfs_i_context (which
should perhaps be renamed to struct netfs_inode).  The struct inode
vfs_inode fields are then removed from the 9p, afs, ceph and cifs inode
structs and vfs_inode is then simply changed to "netfs.inode" in those
filesystems.

Further, rename netfs_i_context to netfs_inode, get rid of the
netfs_inode() function that converted a netfs_i_context pointer to an
inode pointer (that can now be done with &ctx->inode) and rename the
netfs_i_context() function to netfs_inode() (which is now a wrapper
around container_of()).

Most of the changes were done with:

  perl -p -i -e 's/vfs_inode/netfs.inode/'g \
        `git grep -l 'vfs_inode' -- fs/{9p,afs,ceph,cifs}/*.[ch]`

Kees suggested doing it with a pair structure[2] and a special
declarator to insert that into the network filesystem's inode
wrapper[3], but I think it's cleaner to embed it - and then it doesn't
matter if struct randomisation reorders things.

Dave Chinner suggested using a filesystem-specific VFS_I() function in
each filesystem to convert that filesystem's own inode wrapper struct
into the VFS inode struct[4].

Version #2:
 - Fix a couple of missed name changes due to a disabled cifs option.
 - Rename nfs_i_context to nfs_inode
 - Use "netfs" instead of "nic" as the member name in per-fs inode wrapper
   structs.

[ This also undoes commit 507160f46c55 ("netfs: gcc-12: temporarily
  disable '-Wattribute-warning' for now") that is no longer needed ]

Fixes: bc899ee1c898 ("netfs: Add a netfs inode context")
Reported-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
cc: Jonathan Corbet <corbet@lwn.net>
cc: Eric Van Hensbergen <ericvh@gmail.com>
cc: Latchesar Ionkov <lucho@ionkov.net>
cc: Dominique Martinet <asmadeus@codewreck.org>
cc: Christian Schoenebeck <linux_oss@crudebyte.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Ilya Dryomov <idryomov@gmail.com>
cc: Steve French <smfrench@gmail.com>
cc: William Kucharski <william.kucharski@oracle.com>
cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
cc: Dave Chinner <david@fromorbit.com>
cc: linux-doc@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-afs@lists.infradead.org
cc: ceph-devel@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: samba-technical@lists.samba.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-hardening@vger.kernel.org
Link: https://lore.kernel.org/r/d2ad3a3d7bdd794c6efb562d2f2b655fb67756b9.camel@kernel.org/ [1]
Link: https://lore.kernel.org/r/20220517210230.864239-1-keescook@chromium.org/ [2]
Link: https://lore.kernel.org/r/20220518202212.2322058-1-keescook@chromium.org/ [3]
Link: https://lore.kernel.org/r/20220524101205.GI2306852@dread.disaster.area/ [4]
Link: https://lore.kernel.org/r/165296786831.3591209.12111293034669289733.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/165305805651.4094995.7763502506786714216.stgit@warthog.procyon.org.uk # v2
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 9 insertions, 13 deletions

diff --git a/fs/9p/cache.c b/fs/9p/cache.c
index 1c8dc696d516..cebba4eaa0b5 100644
--- a/fs/9p/cache.c
+++ b/fs/9p/cache.c
@@ -62,12 +62,12 @@ void v9fs_cache_inode_get_cookie(struct inode *inode)
 	version = cpu_to_le32(v9inode->qid.version);
 	path = cpu_to_le64(v9inode->qid.path);
 	v9ses = v9fs_inode2v9ses(inode);
-	v9inode->netfs_ctx.cache =
+	v9inode->netfs.cache =
 		fscache_acquire_cookie(v9fs_session_cache(v9ses),
 				       0,
 				       &path, sizeof(path),
 				       &version, sizeof(version),
-				       i_size_read(&v9inode->vfs_inode));
+				       i_size_read(&v9inode->netfs.inode));
 
 	p9_debug(P9_DEBUG_FSC, "inode %p get cookie %p\n",
 		 inode, v9fs_inode_cookie(v9inode));
diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index e28ddf763b3b..0129de2ea31a 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -625,7 +625,7 @@ static void v9fs_inode_init_once(void *foo)
 	struct v9fs_inode *v9inode = (struct v9fs_inode *)foo;
 
 	memset(&v9inode->qid, 0, sizeof(v9inode->qid));
-	inode_init_once(&v9inode->vfs_inode);
+	inode_init_once(&v9inode->netfs.inode);
 }
 
 /**
diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index ec0e8df3b2eb..1b219c21d15e 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -109,11 +109,7 @@ struct v9fs_session_info {
 #define V9FS_INO_INVALID_ATTR 0x01
 
 struct v9fs_inode {
-	struct {
-		/* These must be contiguous */
-		struct inode	vfs_inode;	/* the VFS's inode record */
-		struct netfs_i_context netfs_ctx; /* Netfslib context */
-	};
+	struct netfs_inode netfs; /* Netfslib context and vfs inode */
 	struct p9_qid qid;
 	unsigned int cache_validity;
 	struct p9_fid *writeback_fid;
@@ -122,13 +118,13 @@ struct v9fs_inode {
 
 static inline struct v9fs_inode *V9FS_I(const struct inode *inode)
 {
-	return container_of(inode, struct v9fs_inode, vfs_inode);
+	return container_of(inode, struct v9fs_inode, netfs.inode);
 }
 
 static inline struct fscache_cookie *v9fs_inode_cookie(struct v9fs_inode *v9inode)
 {
 #ifdef CONFIG_9P_FSCACHE
-	return netfs_i_cookie(&v9inode->vfs_inode);
+	return netfs_i_cookie(&v9inode->netfs.inode);
 #else
 	return NULL;
 #endif
diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 8ce82ff1e40a..90c6c1ba03ab 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -140,7 +140,7 @@ static void v9fs_write_to_cache_done(void *priv, ssize_t transferred_or_error,
 	    transferred_or_error != -ENOBUFS) {
 		version = cpu_to_le32(v9inode->qid.version);
 		fscache_invalidate(v9fs_inode_cookie(v9inode), &version,
-				   i_size_read(&v9inode->vfs_inode), 0);
+				   i_size_read(&v9inode->netfs.inode), 0);
 	}
 }
 
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 55367ecb9442..e660c6348b9d 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -234,7 +234,7 @@ struct inode *v9fs_alloc_inode(struct super_block *sb)
 	v9inode->writeback_fid = NULL;
 	v9inode->cache_validity = 0;
 	mutex_init(&v9inode->v_mutex);
-	return &v9inode->vfs_inode;
+	return &v9inode->netfs.inode;
 }
 
 /**
@@ -252,7 +252,7 @@ void v9fs_free_inode(struct inode *inode)
  */
 static void v9fs_set_netfs_context(struct inode *inode)
 {
-	netfs_i_context_init(inode, &v9fs_req_ops);
+	netfs_inode_init(inode, &v9fs_req_ops);
 }
 
 int v9fs_init_inode(struct v9fs_session_info *v9ses,