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 35 extern int overflowuid; 36 extern int overflowgid; 37 38 extern void __bad_uid(void); 39 extern 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 */ 82 extern int fs_overflowuid; 83 extern 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