From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 16 Apr 2005 15:20:36 -0700 Subject: Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip! --- kernel/user.c | 189 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 189 insertions(+) create mode 100644 kernel/user.c (limited to 'kernel/user.c') diff --git a/kernel/user.c b/kernel/user.c new file mode 100644 index 000000000000..734575d55769 --- /dev/null +++ b/kernel/user.c @@ -0,0 +1,189 @@ +/* + * The "user cache". + * + * (C) Copyright 1991-2000 Linus Torvalds + * + * We have a per-user structure to keep track of how many + * processes, files etc the user has claimed, in order to be + * able to have per-user limits for system resources. + */ + +#include +#include +#include +#include +#include + +/* + * UID task count cache, to get fast user lookup in "alloc_uid" + * when changing user ID's (ie setuid() and friends). + */ + +#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 8) +#define UIDHASH_SZ (1 << UIDHASH_BITS) +#define UIDHASH_MASK (UIDHASH_SZ - 1) +#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK) +#define uidhashentry(uid) (uidhash_table + __uidhashfn((uid))) + +static kmem_cache_t *uid_cachep; +static struct list_head uidhash_table[UIDHASH_SZ]; +static DEFINE_SPINLOCK(uidhash_lock); + +struct user_struct root_user = { + .__count = ATOMIC_INIT(1), + .processes = ATOMIC_INIT(1), + .files = ATOMIC_INIT(0), + .sigpending = ATOMIC_INIT(0), + .mq_bytes = 0, + .locked_shm = 0, +#ifdef CONFIG_KEYS + .uid_keyring = &root_user_keyring, + .session_keyring = &root_session_keyring, +#endif +}; + +/* + * These routines must be called with the uidhash spinlock held! + */ +static inline void uid_hash_insert(struct user_struct *up, struct list_head *hashent) +{ + list_add(&up->uidhash_list, hashent); +} + +static inline void uid_hash_remove(struct user_struct *up) +{ + list_del(&up->uidhash_list); +} + +static inline struct user_struct *uid_hash_find(uid_t uid, struct list_head *hashent) +{ + struct list_head *up; + + list_for_each(up, hashent) { + struct user_struct *user; + + user = list_entry(up, struct user_struct, uidhash_list); + + if(user->uid == uid) { + atomic_inc(&user->__count); + return user; + } + } + + return NULL; +} + +/* + * Locate the user_struct for the passed UID. If found, take a ref on it. The + * caller must undo that ref with free_uid(). + * + * If the user_struct could not be found, return NULL. + */ +struct user_struct *find_user(uid_t uid) +{ + struct user_struct *ret; + + spin_lock(&uidhash_lock); + ret = uid_hash_find(uid, uidhashentry(uid)); + spin_unlock(&uidhash_lock); + return ret; +} + +void free_uid(struct user_struct *up) +{ + if (up && atomic_dec_and_lock(&up->__count, &uidhash_lock)) { + uid_hash_remove(up); + key_put(up->uid_keyring); + key_put(up->session_keyring); + kmem_cache_free(uid_cachep, up); + spin_unlock(&uidhash_lock); + } +} + +struct user_struct * alloc_uid(uid_t uid) +{ + struct list_head *hashent = uidhashentry(uid); + struct user_struct *up; + + spin_lock(&uidhash_lock); + up = uid_hash_find(uid, hashent); + spin_unlock(&uidhash_lock); + + if (!up) { + struct user_struct *new; + + new = kmem_cache_alloc(uid_cachep, SLAB_KERNEL); + if (!new) + return NULL; + new->uid = uid; + atomic_set(&new->__count, 1); + atomic_set(&new->processes, 0); + atomic_set(&new->files, 0); + atomic_set(&new->sigpending, 0); + + new->mq_bytes = 0; + new->locked_shm = 0; + + if (alloc_uid_keyring(new) < 0) { + kmem_cache_free(uid_cachep, new); + return NULL; + } + + /* + * Before adding this, check whether we raced + * on adding the same user already.. + */ + spin_lock(&uidhash_lock); + up = uid_hash_find(uid, hashent); + if (up) { + key_put(new->uid_keyring); + key_put(new->session_keyring); + kmem_cache_free(uid_cachep, new); + } else { + uid_hash_insert(new, hashent); + up = new; + } + spin_unlock(&uidhash_lock); + + } + return up; +} + +void switch_uid(struct user_struct *new_user) +{ + struct user_struct *old_user; + + /* What if a process setreuid()'s and this brings the + * new uid over his NPROC rlimit? We can check this now + * cheaply with the new uid cache, so if it matters + * we should be checking for it. -DaveM + */ + old_user = current->user; + atomic_inc(&new_user->processes); + atomic_dec(&old_user->processes); + switch_uid_keyring(new_user); + current->user = new_user; + free_uid(old_user); + suid_keys(current); +} + + +static int __init uid_cache_init(void) +{ + int n; + + uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct), + 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); + + for(n = 0; n < UIDHASH_SZ; ++n) + INIT_LIST_HEAD(uidhash_table + n); + + /* Insert the root user immediately (init already runs as root) */ + spin_lock(&uidhash_lock); + uid_hash_insert(&root_user, uidhashentry(0)); + spin_unlock(&uidhash_lock); + + return 0; +} + +module_init(uid_cache_init); -- cgit v1.2.3-55-g7522