1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_HIGHUID_H
3#define _LINUX_HIGHUID_H
4
5#include <linux/types.h>
6
7/*
8 * general notes:
9 *
10 * CONFIG_UID16 is defined if the given architecture needs to
11 * support backwards compatibility for old system calls.
12 *
13 * kernel code should use uid_t and gid_t at all times when dealing with
14 * kernel-private data.
15 *
16 * old_uid_t and old_gid_t should only be different if CONFIG_UID16 is
17 * defined, else the platform should provide dummy typedefs for them
18 * such that they are equivalent to __kernel_{u,g}id_t.
19 *
20 * uid16_t and gid16_t are used on all architectures. (when dealing
21 * with structures hard coded to 16 bits, such as in filesystems)
22 */
23
24
25/*
26 * This is the "overflow" UID and GID. They are used to signify uid/gid
27 * overflow to old programs when they request uid/gid information but are
28 * using the old 16 bit interfaces.
29 * When you run a libc5 program, it will think that all highuid files or
30 * processes are owned by this uid/gid.
31 * The idea is that it's better to do so than possibly return 0 in lieu of
32 * 65536, etc.
33 */
34
35extern int overflowuid;
36extern int overflowgid;
37
38extern void __bad_uid(void);
39extern void __bad_gid(void);
40
41#define DEFAULT_OVERFLOWUID 65534
42#define DEFAULT_OVERFLOWGID 65534
43
44#ifdef CONFIG_UID16
45
46/* prevent uid mod 65536 effect by returning a default value for high UIDs */
47#define high2lowuid(uid) ((uid) & ~0xFFFF ? (old_uid_t)overflowuid : (old_uid_t)(uid))
48#define high2lowgid(gid) ((gid) & ~0xFFFF ? (old_gid_t)overflowgid : (old_gid_t)(gid))
49/*
50 * -1 is different in 16 bits than it is in 32 bits
51 * these macros are used by chown(), setreuid(), ...,
52 */
53#define low2highuid(uid) ((uid) == (old_uid_t)-1 ? (uid_t)-1 : (uid_t)(uid))
54#define low2highgid(gid) ((gid) == (old_gid_t)-1 ? (gid_t)-1 : (gid_t)(gid))
55
56#define __convert_uid(size, uid) \
57 (size >= sizeof(uid) ? (uid) : high2lowuid(uid))
58#define __convert_gid(size, gid) \
59 (size >= sizeof(gid) ? (gid) : high2lowgid(gid))
60
61
62#else
63
64#define __convert_uid(size, uid) (uid)
65#define __convert_gid(size, gid) (gid)
66
67#endif /* !CONFIG_UID16 */
68
69/* uid/gid input should be always 32bit uid_t */
70#define SET_UID(var, uid) do { (var) = __convert_uid(sizeof(var), (uid)); } while (0)
71#define SET_GID(var, gid) do { (var) = __convert_gid(sizeof(var), (gid)); } while (0)
72
73/*
74 * Everything below this line is needed on all architectures, to deal with
75 * filesystems that only store 16 bits of the UID/GID, etc.
76 */
77
78/*
79 * This is the UID and GID that will get written to disk if a filesystem
80 * only supports 16-bit UIDs and the kernel has a high UID/GID to write
81 */
82extern int fs_overflowuid;
83extern int fs_overflowgid;
84
85#define DEFAULT_FS_OVERFLOWUID 65534
86#define DEFAULT_FS_OVERFLOWGID 65534
87
88/*
89 * Since these macros are used in architectures that only need limited
90 * 16-bit UID back compatibility, we won't use old_uid_t and old_gid_t
91 */
92#define fs_high2lowuid(uid) ((uid) & ~0xFFFF ? (uid16_t)fs_overflowuid : (uid16_t)(uid))
93#define fs_high2lowgid(gid) ((gid) & ~0xFFFF ? (gid16_t)fs_overflowgid : (gid16_t)(gid))
94
95#define low_16_bits(x) ((x) & 0xFFFF)
96#define high_16_bits(x) (((x) & 0xFFFF0000) >> 16)
97
98#endif /* _LINUX_HIGHUID_H */
99