sys_setfsuid [kernel/sys.c]
Sets the user ID that the Linux kernel uses to check for all accesses to the file system. Explicit calls to sys_setfsuid are usually only used by programs such as the Linux NFS server that need to change what user ID is used for file access without a corresponding change in the real and effective user ID. A change in the normal user IDs for a program such as the NFS server is a security hole that can expose it to unwanted signals. Arguments
eax | 138
ebx | User ID. Normally, the value of ebx will shadow the value of the effective user ID. In fact, whenever the effective user ID is changed, file system UID will also be changed to the new value of the effective user ID.
Return values This system call always returns previous group ID. Remarks sys_setfsuid will only succeed if the caller is the superuser or if ebx matches either the real user ID, effective user ID, saved set-user-ID, or the current value of file system UID. Compatibility n/a