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>

1 files changed, 7 insertions, 7 deletions

diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 8c2dc2c762a4..f141f5246163 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -57,7 +57,7 @@ static bool ceph_vxattrcb_layout_exists(struct ceph_inode_info *ci)
 static ssize_t ceph_vxattrcb_layout(struct ceph_inode_info *ci, char *val,
 				    size_t size)
 {
-	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->vfs_inode.i_sb);
+	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->netfs.inode.i_sb);
 	struct ceph_osd_client *osdc = &fsc->client->osdc;
 	struct ceph_string *pool_ns;
 	s64 pool = ci->i_layout.pool_id;
@@ -69,7 +69,7 @@ static ssize_t ceph_vxattrcb_layout(struct ceph_inode_info *ci, char *val,
 
 	pool_ns = ceph_try_get_string(ci->i_layout.pool_ns);
 
-	dout("ceph_vxattrcb_layout %p\n", &ci->vfs_inode);
+	dout("ceph_vxattrcb_layout %p\n", &ci->netfs.inode);
 	down_read(&osdc->lock);
 	pool_name = ceph_pg_pool_name_by_id(osdc->osdmap, pool);
 	if (pool_name) {
@@ -161,7 +161,7 @@ static ssize_t ceph_vxattrcb_layout_pool(struct ceph_inode_info *ci,
 					 char *val, size_t size)
 {
 	ssize_t ret;
-	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->vfs_inode.i_sb);
+	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->netfs.inode.i_sb);
 	struct ceph_osd_client *osdc = &fsc->client->osdc;
 	s64 pool = ci->i_layout.pool_id;
 	const char *pool_name;
@@ -313,7 +313,7 @@ static ssize_t ceph_vxattrcb_snap_btime(struct ceph_inode_info *ci, char *val,
 static ssize_t ceph_vxattrcb_cluster_fsid(struct ceph_inode_info *ci,
 					  char *val, size_t size)
 {
-	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->vfs_inode.i_sb);
+	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->netfs.inode.i_sb);
 
 	return ceph_fmt_xattr(val, size, "%pU", &fsc->client->fsid);
 }
@@ -321,7 +321,7 @@ static ssize_t ceph_vxattrcb_cluster_fsid(struct ceph_inode_info *ci,
 static ssize_t ceph_vxattrcb_client_id(struct ceph_inode_info *ci,
 				       char *val, size_t size)
 {
-	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->vfs_inode.i_sb);
+	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->netfs.inode.i_sb);
 
 	return ceph_fmt_xattr(val, size, "client%lld",
 			      ceph_client_gid(fsc->client));
@@ -629,7 +629,7 @@ static int __set_xattr(struct ceph_inode_info *ci,
 	}
 
 	dout("__set_xattr_val added %llx.%llx xattr %p %.*s=%.*s\n",
-	     ceph_vinop(&ci->vfs_inode), xattr, name_len, name, val_len, val);
+	     ceph_vinop(&ci->netfs.inode), xattr, name_len, name, val_len, val);
 
 	return 0;
 }
@@ -871,7 +871,7 @@ struct ceph_buffer *__ceph_build_xattrs_blob(struct ceph_inode_info *ci)
 	struct ceph_buffer *old_blob = NULL;
 	void *dest;
 
-	dout("__build_xattrs_blob %p\n", &ci->vfs_inode);
+	dout("__build_xattrs_blob %p\n", &ci->netfs.inode);
 	if (ci->i_xattrs.dirty) {
 		int need = __get_required_blob_size(ci, 0, 0);