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authorDavid Howells <dhowells@redhat.com>2022-06-09 21:46:04 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2022-06-09 13:55:00 -0700
commit874c8ca1e60b2c564a48f7e7acc40d328d5c8733 (patch)
treef56e0d0a842cc459f8a4a062c88dd54a869d82c5 /Documentation
parent3d9f55c57bc3659f986acc421eac431ff6edcc83 (diff)
downloadlinux-874c8ca1e60b2c564a48f7e7acc40d328d5c8733.tar.bz2
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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/netfs_library.rst37
1 files changed, 18 insertions, 19 deletions
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)::