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>

8 files changed, 28 insertions, 32 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 12c872800326..c85d9a378325 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -377,7 +377,7 @@ cifs_alloc_inode(struct super_block *sb)
 	cifs_inode->flags = 0;
 	spin_lock_init(&cifs_inode->writers_lock);
 	cifs_inode->writers = 0;
-	cifs_inode->vfs_inode.i_blkbits = 14;  /* 2**14 = CIFS_MAX_MSGSIZE */
+	cifs_inode->netfs.inode.i_blkbits = 14;  /* 2**14 = CIFS_MAX_MSGSIZE */
 	cifs_inode->server_eof = 0;
 	cifs_inode->uniqueid = 0;
 	cifs_inode->createtime = 0;
@@ -389,12 +389,12 @@ cifs_alloc_inode(struct super_block *sb)
 	 * Can not set i_flags here - they get immediately overwritten to zero
 	 * by the VFS.
 	 */
-	/* cifs_inode->vfs_inode.i_flags = S_NOATIME | S_NOCMTIME; */
+	/* cifs_inode->netfs.inode.i_flags = S_NOATIME | S_NOCMTIME; */
 	INIT_LIST_HEAD(&cifs_inode->openFileList);
 	INIT_LIST_HEAD(&cifs_inode->llist);
 	INIT_LIST_HEAD(&cifs_inode->deferred_closes);
 	spin_lock_init(&cifs_inode->deferred_lock);
-	return &cifs_inode->vfs_inode;
+	return &cifs_inode->netfs.inode;
 }
 
 static void
@@ -1418,7 +1418,7 @@ cifs_init_once(void *inode)
 {
 	struct cifsInodeInfo *cifsi = inode;
 
-	inode_init_once(&cifsi->vfs_inode);
+	inode_init_once(&cifsi->netfs.inode);
 	init_rwsem(&cifsi->lock_sem);
 }
 
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index f873379066c7..e7737166e5b8 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1479,20 +1479,16 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file);
 #define CIFS_CACHE_RW_FLG	(CIFS_CACHE_READ_FLG | CIFS_CACHE_WRITE_FLG)
 #define CIFS_CACHE_RHW_FLG	(CIFS_CACHE_RW_FLG | CIFS_CACHE_HANDLE_FLG)
 
-#define CIFS_CACHE_READ(cinode) ((cinode->oplock & CIFS_CACHE_READ_FLG) || (CIFS_SB(cinode->vfs_inode.i_sb)->mnt_cifs_flags & CIFS_MOUNT_RO_CACHE))
+#define CIFS_CACHE_READ(cinode) ((cinode->oplock & CIFS_CACHE_READ_FLG) || (CIFS_SB(cinode->netfs.inode.i_sb)->mnt_cifs_flags & CIFS_MOUNT_RO_CACHE))
 #define CIFS_CACHE_HANDLE(cinode) (cinode->oplock & CIFS_CACHE_HANDLE_FLG)
-#define CIFS_CACHE_WRITE(cinode) ((cinode->oplock & CIFS_CACHE_WRITE_FLG) || (CIFS_SB(cinode->vfs_inode.i_sb)->mnt_cifs_flags & CIFS_MOUNT_RW_CACHE))
+#define CIFS_CACHE_WRITE(cinode) ((cinode->oplock & CIFS_CACHE_WRITE_FLG) || (CIFS_SB(cinode->netfs.inode.i_sb)->mnt_cifs_flags & CIFS_MOUNT_RW_CACHE))
 
 /*
  * One of these for each file inode
  */
 
 struct cifsInodeInfo {
-	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 */
 	bool can_cache_brlcks;
 	struct list_head llist;	/* locks helb by this inode */
 	/*
@@ -1531,7 +1527,7 @@ struct cifsInodeInfo {
 static inline struct cifsInodeInfo *
 CIFS_I(struct inode *inode)
 {
-	return container_of(inode, struct cifsInodeInfo, vfs_inode);
+	return container_of(inode, struct cifsInodeInfo, netfs.inode);
 }
 
 static inline struct cifs_sb_info *
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 1618e0537d58..e64cda7a7610 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2004,7 +2004,7 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode,
 					bool fsuid_only)
 {
 	struct cifsFileInfo *open_file = NULL;
-	struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
+	struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_inode->netfs.inode.i_sb);
 
 	/* only filter by fsuid on multiuser mounts */
 	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER))
@@ -2060,7 +2060,7 @@ cifs_get_writable_file(struct cifsInodeInfo *cifs_inode, int flags,
 		return rc;
 	}
 
-	cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
+	cifs_sb = CIFS_SB(cifs_inode->netfs.inode.i_sb);
 
 	/* only filter by fsuid on multiuser mounts */
 	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER))
@@ -4669,14 +4669,14 @@ bool is_size_safe_to_change(struct cifsInodeInfo *cifsInode, __u64 end_of_file)
 		/* This inode is open for write at least once */
 		struct cifs_sb_info *cifs_sb;
 
-		cifs_sb = CIFS_SB(cifsInode->vfs_inode.i_sb);
+		cifs_sb = CIFS_SB(cifsInode->netfs.inode.i_sb);
 		if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_DIRECT_IO) {
 			/* since no page cache to corrupt on directio
 			we can change size safely */
 			return true;
 		}
 
-		if (i_size_read(&cifsInode->vfs_inode) < end_of_file)
+		if (i_size_read(&cifsInode->netfs.inode) < end_of_file)
 			return true;
 
 		return false;
diff --git a/fs/cifs/fscache.c b/fs/cifs/fscache.c
index a638b29e9062..23ef56f55ce5 100644
--- a/fs/cifs/fscache.c
+++ b/fs/cifs/fscache.c
@@ -101,13 +101,13 @@ void cifs_fscache_get_inode_cookie(struct inode *inode)
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
 
-	cifs_fscache_fill_coherency(&cifsi->vfs_inode, &cd);
+	cifs_fscache_fill_coherency(&cifsi->netfs.inode, &cd);
 
-	cifsi->netfs_ctx.cache =
+	cifsi->netfs.cache =
 		fscache_acquire_cookie(tcon->fscache, 0,
 				       &cifsi->uniqueid, sizeof(cifsi->uniqueid),
 				       &cd, sizeof(cd),
-				       i_size_read(&cifsi->vfs_inode));
+				       i_size_read(&cifsi->netfs.inode));
 }
 
 void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update)
@@ -131,7 +131,7 @@ void cifs_fscache_release_inode_cookie(struct inode *inode)
 	if (cookie) {
 		cifs_dbg(FYI, "%s: (0x%p)\n", __func__, cookie);
 		fscache_relinquish_cookie(cookie, false);
-		cifsi->netfs_ctx.cache = NULL;
+		cifsi->netfs.cache = NULL;
 	}
 }
 
diff --git a/fs/cifs/fscache.h b/fs/cifs/fscache.h
index 52355c0912ae..ab9a51d0125c 100644
--- a/fs/cifs/fscache.h
+++ b/fs/cifs/fscache.h
@@ -52,10 +52,10 @@ void cifs_fscache_fill_coherency(struct inode *inode,
 	struct cifsInodeInfo *cifsi = CIFS_I(inode);
 
 	memset(cd, 0, sizeof(*cd));
-	cd->last_write_time_sec   = cpu_to_le64(cifsi->vfs_inode.i_mtime.tv_sec);
-	cd->last_write_time_nsec  = cpu_to_le32(cifsi->vfs_inode.i_mtime.tv_nsec);
-	cd->last_change_time_sec  = cpu_to_le64(cifsi->vfs_inode.i_ctime.tv_sec);
-	cd->last_change_time_nsec = cpu_to_le32(cifsi->vfs_inode.i_ctime.tv_nsec);
+	cd->last_write_time_sec   = cpu_to_le64(cifsi->netfs.inode.i_mtime.tv_sec);
+	cd->last_write_time_nsec  = cpu_to_le32(cifsi->netfs.inode.i_mtime.tv_nsec);
+	cd->last_change_time_sec  = cpu_to_le64(cifsi->netfs.inode.i_ctime.tv_sec);
+	cd->last_change_time_nsec = cpu_to_le32(cifsi->netfs.inode.i_ctime.tv_nsec);
 }
 
 
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 2f9e7d2f81b6..81da81e18553 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -115,7 +115,7 @@ cifs_revalidate_cache(struct inode *inode, struct cifs_fattr *fattr)
 		 __func__, cifs_i->uniqueid);
 	set_bit(CIFS_INO_INVALID_MAPPING, &cifs_i->flags);
 	/* Invalidate fscache cookie */
-	cifs_fscache_fill_coherency(&cifs_i->vfs_inode, &cd);
+	cifs_fscache_fill_coherency(&cifs_i->netfs.inode, &cd);
 	fscache_invalidate(cifs_inode_cookie(inode), &cd, i_size_read(inode), 0);
 }
 
@@ -2499,7 +2499,7 @@ int cifs_fiemap(struct inode *inode, struct fiemap_extent_info *fei, u64 start,
 		u64 len)
 {
 	struct cifsInodeInfo *cifs_i = CIFS_I(inode);
-	struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_i->vfs_inode.i_sb);
+	struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_i->netfs.inode.i_sb);
 	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
 	struct TCP_Server_Info *server = tcon->ses->server;
 	struct cifsFileInfo *cfile;
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 35962a1a23b9..cbc3b433f502 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -537,11 +537,11 @@ void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock)
 	if (oplock == OPLOCK_EXCLUSIVE) {
 		cinode->oplock = CIFS_CACHE_WRITE_FLG | CIFS_CACHE_READ_FLG;
 		cifs_dbg(FYI, "Exclusive Oplock granted on inode %p\n",
-			 &cinode->vfs_inode);
+			 &cinode->netfs.inode);
 	} else if (oplock == OPLOCK_READ) {
 		cinode->oplock = CIFS_CACHE_READ_FLG;
 		cifs_dbg(FYI, "Level II Oplock granted on inode %p\n",
-			 &cinode->vfs_inode);
+			 &cinode->netfs.inode);
 	} else
 		cinode->oplock = 0;
 }
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 98a76fa791c0..8543cafdfd34 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -4260,15 +4260,15 @@ smb2_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock,
 	if (oplock == SMB2_OPLOCK_LEVEL_BATCH) {
 		cinode->oplock = CIFS_CACHE_RHW_FLG;
 		cifs_dbg(FYI, "Batch Oplock granted on inode %p\n",
-			 &cinode->vfs_inode);
+			 &cinode->netfs.inode);
 	} else if (oplock == SMB2_OPLOCK_LEVEL_EXCLUSIVE) {
 		cinode->oplock = CIFS_CACHE_RW_FLG;
 		cifs_dbg(FYI, "Exclusive Oplock granted on inode %p\n",
-			 &cinode->vfs_inode);
+			 &cinode->netfs.inode);
 	} else if (oplock == SMB2_OPLOCK_LEVEL_II) {
 		cinode->oplock = CIFS_CACHE_READ_FLG;
 		cifs_dbg(FYI, "Level II Oplock granted on inode %p\n",
-			 &cinode->vfs_inode);
+			 &cinode->netfs.inode);
 	} else
 		cinode->oplock = 0;
 }
@@ -4307,7 +4307,7 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock,
 
 	cinode->oplock = new_oplock;
 	cifs_dbg(FYI, "%s Lease granted on inode %p\n", message,
-		 &cinode->vfs_inode);
+		 &cinode->netfs.inode);
 }
 
 static void