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, 16 insertions, 16 deletions

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 79f6b74336d2..56ae5cd5184f 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -109,7 +109,7 @@ struct afs_lookup_cookie {
  */
 static void afs_dir_read_cleanup(struct afs_read *req)
 {
-	struct address_space *mapping = req->vnode->vfs_inode.i_mapping;
+	struct address_space *mapping = req->vnode->netfs.inode.i_mapping;
 	struct folio *folio;
 	pgoff_t last = req->nr_pages - 1;
 
@@ -153,7 +153,7 @@ static bool afs_dir_check_folio(struct afs_vnode *dvnode, struct folio *folio,
 		block = kmap_local_folio(folio, offset);
 		if (block->hdr.magic != AFS_DIR_MAGIC) {
 			printk("kAFS: %s(%lx): [%llx] bad magic %zx/%zx is %04hx\n",
-			       __func__, dvnode->vfs_inode.i_ino,
+			       __func__, dvnode->netfs.inode.i_ino,
 			       pos, offset, size, ntohs(block->hdr.magic));
 			trace_afs_dir_check_failed(dvnode, pos + offset, i_size);
 			kunmap_local(block);
@@ -183,7 +183,7 @@ error:
 static void afs_dir_dump(struct afs_vnode *dvnode, struct afs_read *req)
 {
 	union afs_xdr_dir_block *block;
-	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct address_space *mapping = dvnode->netfs.inode.i_mapping;
 	struct folio *folio;
 	pgoff_t last = req->nr_pages - 1;
 	size_t offset, size;
@@ -217,7 +217,7 @@ static void afs_dir_dump(struct afs_vnode *dvnode, struct afs_read *req)
  */
 static int afs_dir_check(struct afs_vnode *dvnode, struct afs_read *req)
 {
-	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct address_space *mapping = dvnode->netfs.inode.i_mapping;
 	struct folio *folio;
 	pgoff_t last = req->nr_pages - 1;
 	int ret = 0;
@@ -269,7 +269,7 @@ static int afs_dir_open(struct inode *inode, struct file *file)
 static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 	__acquires(&dvnode->validate_lock)
 {
-	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct address_space *mapping = dvnode->netfs.inode.i_mapping;
 	struct afs_read *req;
 	loff_t i_size;
 	int nr_pages, i;
@@ -287,7 +287,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 	req->cleanup = afs_dir_read_cleanup;
 
 expand:
-	i_size = i_size_read(&dvnode->vfs_inode);
+	i_size = i_size_read(&dvnode->netfs.inode);
 	if (i_size < 2048) {
 		ret = afs_bad(dvnode, afs_file_error_dir_small);
 		goto error;
@@ -305,7 +305,7 @@ expand:
 	req->actual_len = i_size; /* May change */
 	req->len = nr_pages * PAGE_SIZE; /* We can ask for more than there is */
 	req->data_version = dvnode->status.data_version; /* May change */
-	iov_iter_xarray(&req->def_iter, READ, &dvnode->vfs_inode.i_mapping->i_pages,
+	iov_iter_xarray(&req->def_iter, READ, &dvnode->netfs.inode.i_mapping->i_pages,
 			0, i_size);
 	req->iter = &req->def_iter;
 
@@ -897,7 +897,7 @@ static struct inode *afs_do_lookup(struct inode *dir, struct dentry *dentry,
 
 out_op:
 	if (op->error == 0) {
-		inode = &op->file[1].vnode->vfs_inode;
+		inode = &op->file[1].vnode->netfs.inode;
 		op->file[1].vnode = NULL;
 	}
 
@@ -1139,7 +1139,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 	afs_stat_v(dir, n_reval);
 
 	/* search the directory for this vnode */
-	ret = afs_do_lookup_one(&dir->vfs_inode, dentry, &fid, key, &dir_version);
+	ret = afs_do_lookup_one(&dir->netfs.inode, dentry, &fid, key, &dir_version);
 	switch (ret) {
 	case 0:
 		/* the filename maps to something */
@@ -1170,7 +1170,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 			_debug("%pd: file deleted (uq %u -> %u I:%u)",
 			       dentry, fid.unique,
 			       vnode->fid.unique,
-			       vnode->vfs_inode.i_generation);
+			       vnode->netfs.inode.i_generation);
 			goto not_found;
 		}
 		goto out_valid;
@@ -1368,7 +1368,7 @@ static void afs_dir_remove_subdir(struct dentry *dentry)
 	if (d_really_is_positive(dentry)) {
 		struct afs_vnode *vnode = AFS_FS_I(d_inode(dentry));
 
-		clear_nlink(&vnode->vfs_inode);
+		clear_nlink(&vnode->netfs.inode);
 		set_bit(AFS_VNODE_DELETED, &vnode->flags);
 		clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
 		clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
@@ -1487,8 +1487,8 @@ static void afs_dir_remove_link(struct afs_operation *op)
 		/* Already done */
 	} else if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) {
 		write_seqlock(&vnode->cb_lock);
-		drop_nlink(&vnode->vfs_inode);
-		if (vnode->vfs_inode.i_nlink == 0) {
+		drop_nlink(&vnode->netfs.inode);
+		if (vnode->netfs.inode.i_nlink == 0) {
 			set_bit(AFS_VNODE_DELETED, &vnode->flags);
 			__afs_break_callback(vnode, afs_cb_break_for_unlink);
 		}
@@ -1504,7 +1504,7 @@ static void afs_dir_remove_link(struct afs_operation *op)
 			op->error = ret;
 	}
 
-	_debug("nlink %d [val %d]", vnode->vfs_inode.i_nlink, op->error);
+	_debug("nlink %d [val %d]", vnode->netfs.inode.i_nlink, op->error);
 }
 
 static void afs_unlink_success(struct afs_operation *op)
@@ -1680,8 +1680,8 @@ static void afs_link_success(struct afs_operation *op)
 	afs_update_dentry_version(op, dvp, op->dentry);
 	if (op->dentry_2->d_parent == op->dentry->d_parent)
 		afs_update_dentry_version(op, dvp, op->dentry_2);
-	ihold(&vp->vnode->vfs_inode);
-	d_instantiate(op->dentry, &vp->vnode->vfs_inode);
+	ihold(&vp->vnode->netfs.inode);
+	d_instantiate(op->dentry, &vp->vnode->netfs.inode);
 }
 
 static void afs_link_put(struct afs_operation *op)