kernel/uid16.c

File Facts

System

Linux kernel

Corpus path

kernel/uid16.c

Extension

.c

Size

5198 bytes

Lines

222

Domain

Core OS

Bucket

Scheduler, Processes, Timers, Sync, And Syscalls

Inferred role

Core OS: syscall or user/kernel boundary

Status

core implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

• Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.
• Defines or participates in a user/kernel boundary; inspect argument validation, copy_from_user/copy_to_user, credentials, and dispatch target.
• Touches user memory; correctness depends on fault-safe copying and privilege boundary handling.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• linux/mm.h
• linux/mman.h
• linux/notifier.h
• linux/reboot.h
• linux/prctl.h
• linux/capability.h
• linux/init.h
• linux/highuid.h
• linux/security.h
• linux/cred.h
• linux/syscalls.h
• linux/uaccess.h
• uid16.h

Detected Declarations

• syscall chown16
• syscall lchown16
• syscall fchown16
• syscall setregid16
• syscall setgid16
• syscall setreuid16
• syscall setuid16
• syscall setresuid16
• syscall getresuid16
• syscall setresgid16
• syscall getresgid16
• syscall setfsuid16
• syscall setfsgid16
• syscall getgroups16
• syscall setgroups16
• syscall getuid16
• syscall geteuid16
• syscall getgid16
• syscall getegid16
• function groups16_to_user
• function groups16_from_user

Annotated Snippet

SYSCALL_DEFINE3(chown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
{
	return ksys_chown(filename, low2highuid(user), low2highgid(group));
}

SYSCALL_DEFINE3(lchown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
{
	return ksys_lchown(filename, low2highuid(user), low2highgid(group));
}

SYSCALL_DEFINE3(fchown16, unsigned int, fd, old_uid_t, user, old_gid_t, group)
{
	return ksys_fchown(fd, low2highuid(user), low2highgid(group));
}

SYSCALL_DEFINE2(setregid16, old_gid_t, rgid, old_gid_t, egid)
{
	return __sys_setregid(low2highgid(rgid), low2highgid(egid));
}

SYSCALL_DEFINE1(setgid16, old_gid_t, gid)
{
	return __sys_setgid(low2highgid(gid));
}

SYSCALL_DEFINE2(setreuid16, old_uid_t, ruid, old_uid_t, euid)
{
	return __sys_setreuid(low2highuid(ruid), low2highuid(euid));
}

SYSCALL_DEFINE1(setuid16, old_uid_t, uid)
{
	return __sys_setuid(low2highuid(uid));
}

SYSCALL_DEFINE3(setresuid16, old_uid_t, ruid, old_uid_t, euid, old_uid_t, suid)
{
	return __sys_setresuid(low2highuid(ruid), low2highuid(euid),
				 low2highuid(suid));
}

SYSCALL_DEFINE3(getresuid16, old_uid_t __user *, ruidp, old_uid_t __user *, euidp, old_uid_t __user *, suidp)
{
	const struct cred *cred = current_cred();
	int retval;
	old_uid_t ruid, euid, suid;

	ruid = high2lowuid(from_kuid_munged(cred->user_ns, cred->uid));
	euid = high2lowuid(from_kuid_munged(cred->user_ns, cred->euid));
	suid = high2lowuid(from_kuid_munged(cred->user_ns, cred->suid));

	if (!(retval   = put_user(ruid, ruidp)) &&
	    !(retval   = put_user(euid, euidp)))
		retval = put_user(suid, suidp);

	return retval;
}

SYSCALL_DEFINE3(setresgid16, old_gid_t, rgid, old_gid_t, egid, old_gid_t, sgid)
{
	return __sys_setresgid(low2highgid(rgid), low2highgid(egid),
				 low2highgid(sgid));
}

SYSCALL_DEFINE3(getresgid16, old_gid_t __user *, rgidp, old_gid_t __user *, egidp, old_gid_t __user *, sgidp)
{
	const struct cred *cred = current_cred();
	int retval;
	old_gid_t rgid, egid, sgid;

	rgid = high2lowgid(from_kgid_munged(cred->user_ns, cred->gid));
	egid = high2lowgid(from_kgid_munged(cred->user_ns, cred->egid));
	sgid = high2lowgid(from_kgid_munged(cred->user_ns, cred->sgid));

	if (!(retval   = put_user(rgid, rgidp)) &&
	    !(retval   = put_user(egid, egidp)))
		retval = put_user(sgid, sgidp);

	return retval;
}

SYSCALL_DEFINE1(setfsuid16, old_uid_t, uid)
{
	return __sys_setfsuid(low2highuid(uid));
}

SYSCALL_DEFINE1(setfsgid16, old_gid_t, gid)
{
	return __sys_setfsgid(low2highgid(gid));
}

Annotation

• Immediate include surface: `linux/mm.h`, `linux/mman.h`, `linux/notifier.h`, `linux/reboot.h`, `linux/prctl.h`, `linux/capability.h`, `linux/init.h`, `linux/highuid.h`.
• Detected declarations: `syscall chown16`, `syscall lchown16`, `syscall fchown16`, `syscall setregid16`, `syscall setgid16`, `syscall setreuid16`, `syscall setuid16`, `syscall setresuid16`, `syscall getresuid16`, `syscall setresgid16`.
• Atlas domain: Core OS / Scheduler, Processes, Timers, Sync, And Syscalls.
• Implementation status: core implementation candidate.
• This snippet crosses the user/kernel memory boundary; validate fault handling and access checks before translating the pattern.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.