From 874c8ca1e60b2c564a48f7e7acc40d328d5c8733 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 9 Jun 2022 21:46:04 +0100 Subject: 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 Signed-off-by: David Howells Reviewed-by: Jeff Layton Reviewed-by: Kees Cook Reviewed-by: Xiubo Li cc: Jonathan Corbet cc: Eric Van Hensbergen cc: Latchesar Ionkov cc: Dominique Martinet cc: Christian Schoenebeck cc: Marc Dionne cc: Ilya Dryomov cc: Steve French cc: William Kucharski cc: "Matthew Wilcox (Oracle)" cc: Dave Chinner 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 --- Documentation/filesystems/netfs_library.rst | 37 ++++++++++++++--------------- 1 file changed, 18 insertions(+), 19 deletions(-) (limited to 'Documentation') diff --git a/Documentation/filesystems/netfs_library.rst b/Documentation/filesystems/netfs_library.rst index a80a59941d2f..3276c3d55142 100644 --- a/Documentation/filesystems/netfs_library.rst +++ b/Documentation/filesystems/netfs_library.rst @@ -37,30 +37,31 @@ The network filesystem helper library needs a place to store a bit of state for its use on each netfs inode it is helping to manage. To this end, a context structure is defined:: - struct netfs_i_context { + struct netfs_inode { + struct inode inode; const struct netfs_request_ops *ops; - struct fscache_cookie *cache; + struct fscache_cookie *cache; }; -A network filesystem that wants to use netfs lib must place one of these -directly after the VFS ``struct inode`` it allocates, usually as part of its -own struct. This can be done in a way similar to the following:: +A network filesystem that wants to use netfs lib must place one of these in its +inode wrapper struct instead of the VFS ``struct inode``. This can be done in +a way similar to the following:: struct my_inode { - struct { - /* These must be contiguous */ - struct inode vfs_inode; - struct netfs_i_context netfs_ctx; - }; + struct netfs_inode netfs; /* Netfslib context and vfs inode */ ... }; -This allows netfslib to find its state by simple offset from the inode pointer, -thereby allowing the netfslib helper functions to be pointed to directly by the -VFS/VM operation tables. +This allows netfslib to find its state by using ``container_of()`` from the +inode pointer, thereby allowing the netfslib helper functions to be pointed to +directly by the VFS/VM operation tables. The structure contains the following fields: + * ``inode`` + + The VFS inode structure. + * ``ops`` The set of operations provided by the network filesystem to netfslib. @@ -78,14 +79,12 @@ To help deal with the per-inode context, a number helper functions are provided. Firstly, a function to perform basic initialisation on a context and set the operations table pointer:: - void netfs_i_context_init(struct inode *inode, - const struct netfs_request_ops *ops); + void netfs_inode_init(struct inode *inode, + const struct netfs_request_ops *ops); -then two functions to cast between the VFS inode structure and the netfs -context:: +then a function to cast from the VFS inode structure to the netfs context:: - struct netfs_i_context *netfs_i_context(struct inode *inode); - struct inode *netfs_inode(struct netfs_i_context *ctx); + struct netfs_inode *netfs_node(struct inode *inode); and finally, a function to get the cache cookie pointer from the context attached to an inode (or NULL if fscache is disabled):: -- cgit v1.2.3