e6c61d5d44
[ Upstream commit c0a744dcaa29e9537e8607ae9c965ad936124a4d ]
There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].
Use an anonymous union with a couple of anonymous structs in order to
keep userspace unchanged:
$ pahole -C nfs_fhbase_new fs/nfsd/nfsfh.o
struct nfs_fhbase_new {
union {
struct {
__u8 fb_version_aux; /* 0 1 */
__u8 fb_auth_type_aux; /* 1 1 */
__u8 fb_fsid_type_aux; /* 2 1 */
__u8 fb_fileid_type_aux; /* 3 1 */
__u32 fb_auth[1]; /* 4 4 */
}; /* 0 8 */
struct {
__u8 fb_version; /* 0 1 */
__u8 fb_auth_type; /* 1 1 */
__u8 fb_fsid_type; /* 2 1 */
__u8 fb_fileid_type; /* 3 1 */
__u32 fb_auth_flex[0]; /* 4 0 */
}; /* 0 4 */
}; /* 0 8 */
/* size: 8, cachelines: 1, members: 1 */
/* last cacheline: 8 bytes */
};
Also, this helps with the ongoing efforts to enable -Warray-bounds by
fixing the following warnings:
fs/nfsd/nfsfh.c: In function ‘nfsd_set_fh_dentry’:
fs/nfsd/nfsfh.c:191:41: warning: array subscript 1 is above array bounds of ‘__u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
191 | ntohl((__force __be32)fh->fh_fsid[1])));
| ~~~~~~~~~~~^~~
./include/linux/kdev_t.h:12:46: note: in definition of macro ‘MKDEV’
12 | #define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))
| ^~
./include/uapi/linux/byteorder/little_endian.h:40:26: note: in expansion of macro ‘__swab32’
40 | #define __be32_to_cpu(x) __swab32((__force __u32)(__be32)(x))
| ^~~~~~~~
./include/linux/byteorder/generic.h:136:21: note: in expansion of macro ‘__be32_to_cpu’
136 | #define ___ntohl(x) __be32_to_cpu(x)
| ^~~~~~~~~~~~~
./include/linux/byteorder/generic.h:140:18: note: in expansion of macro ‘___ntohl’
140 | #define ntohl(x) ___ntohl(x)
| ^~~~~~~~
fs/nfsd/nfsfh.c:191:8: note: in expansion of macro ‘ntohl’
191 | ntohl((__force __be32)fh->fh_fsid[1])));
| ^~~~~
fs/nfsd/nfsfh.c:192:32: warning: array subscript 2 is above array bounds of ‘__u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
192 | fh->fh_fsid[1] = fh->fh_fsid[2];
| ~~~~~~~~~~~^~~
fs/nfsd/nfsfh.c:192:15: warning: array subscript 1 is above array bounds of ‘__u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
192 | fh->fh_fsid[1] = fh->fh_fsid[2];
| ~~~~~~~~~~~^~~
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
116 lines
3.7 KiB
C
Executable file
116 lines
3.7 KiB
C
Executable file
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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/*
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* This file describes the layout of the file handles as passed
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* over the wire.
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*
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* Copyright (C) 1995, 1996, 1997 Olaf Kirch <okir@monad.swb.de>
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*/
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#ifndef _UAPI_LINUX_NFSD_FH_H
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#define _UAPI_LINUX_NFSD_FH_H
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#include <linux/types.h>
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#include <linux/nfs.h>
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#include <linux/nfs2.h>
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#include <linux/nfs3.h>
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#include <linux/nfs4.h>
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/*
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* This is the old "dentry style" Linux NFSv2 file handle.
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*
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* The xino and xdev fields are currently used to transport the
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* ino/dev of the exported inode.
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*/
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struct nfs_fhbase_old {
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__u32 fb_dcookie; /* dentry cookie - always 0xfeebbaca */
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__u32 fb_ino; /* our inode number */
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__u32 fb_dirino; /* dir inode number, 0 for directories */
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__u32 fb_dev; /* our device */
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__u32 fb_xdev;
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__u32 fb_xino;
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__u32 fb_generation;
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};
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/*
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* This is the new flexible, extensible style NFSv2/v3/v4 file handle.
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* by Neil Brown <neilb@cse.unsw.edu.au> - March 2000
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*
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* The file handle starts with a sequence of four-byte words.
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* The first word contains a version number (1) and three descriptor bytes
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* that tell how the remaining 3 variable length fields should be handled.
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* These three bytes are auth_type, fsid_type and fileid_type.
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*
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* All four-byte values are in host-byte-order.
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*
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* The auth_type field is deprecated and must be set to 0.
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*
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* The fsid_type identifies how the filesystem (or export point) is
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* encoded.
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* Current values:
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* 0 - 4 byte device id (ms-2-bytes major, ls-2-bytes minor), 4byte inode number
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* NOTE: we cannot use the kdev_t device id value, because kdev_t.h
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* says we mustn't. We must break it up and reassemble.
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* 1 - 4 byte user specified identifier
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* 2 - 4 byte major, 4 byte minor, 4 byte inode number - DEPRECATED
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* 3 - 4 byte device id, encoded for user-space, 4 byte inode number
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* 4 - 4 byte inode number and 4 byte uuid
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* 5 - 8 byte uuid
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* 6 - 16 byte uuid
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* 7 - 8 byte inode number and 16 byte uuid
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*
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* The fileid_type identified how the file within the filesystem is encoded.
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* The values for this field are filesystem specific, exccept that
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* filesystems must not use the values '0' or '0xff'. 'See enum fid_type'
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* in include/linux/exportfs.h for currently registered values.
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*/
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struct nfs_fhbase_new {
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union {
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struct {
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__u8 fb_version_aux; /* == 1, even => nfs_fhbase_old */
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__u8 fb_auth_type_aux;
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__u8 fb_fsid_type_aux;
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__u8 fb_fileid_type_aux;
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__u32 fb_auth[1];
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/* __u32 fb_fsid[0]; floating */
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/* __u32 fb_fileid[0]; floating */
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};
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struct {
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__u8 fb_version; /* == 1, even => nfs_fhbase_old */
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__u8 fb_auth_type;
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__u8 fb_fsid_type;
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__u8 fb_fileid_type;
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__u32 fb_auth_flex[]; /* flexible-array member */
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};
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};
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};
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struct knfsd_fh {
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unsigned int fh_size; /* significant for NFSv3.
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* Points to the current size while building
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* a new file handle
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*/
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union {
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struct nfs_fhbase_old fh_old;
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__u32 fh_pad[NFS4_FHSIZE/4];
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struct nfs_fhbase_new fh_new;
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} fh_base;
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};
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#define ofh_dcookie fh_base.fh_old.fb_dcookie
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#define ofh_ino fh_base.fh_old.fb_ino
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#define ofh_dirino fh_base.fh_old.fb_dirino
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#define ofh_dev fh_base.fh_old.fb_dev
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#define ofh_xdev fh_base.fh_old.fb_xdev
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#define ofh_xino fh_base.fh_old.fb_xino
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#define ofh_generation fh_base.fh_old.fb_generation
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#define fh_version fh_base.fh_new.fb_version
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#define fh_fsid_type fh_base.fh_new.fb_fsid_type
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#define fh_auth_type fh_base.fh_new.fb_auth_type
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#define fh_fileid_type fh_base.fh_new.fb_fileid_type
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#define fh_fsid fh_base.fh_new.fb_auth_flex
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/* Do not use, provided for userspace compatiblity. */
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#define fh_auth fh_base.fh_new.fb_auth
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#endif /* _UAPI_LINUX_NFSD_FH_H */
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