1 files changed, 231 insertions, 527 deletions

diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index 0fb15bbbe43c..5cbd00e74067 100644
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -42,135 +42,27 @@ static const struct cifs_sid sid_authusers = {
 /* group users */
 static const struct cifs_sid sid_user = {1, 2 , {0, 0, 0, 0, 0, 5}, {} };
 
-const struct cred *root_cred;
-
-static void
-shrink_idmap_tree(struct rb_root *root, int nr_to_scan, int *nr_rem,
-			int *nr_del)
-{
-	struct rb_node *node;
-	struct rb_node *tmp;
-	struct cifs_sid_id *psidid;
-
-	node = rb_first(root);
-	while (node) {
-		tmp = node;
-		node = rb_next(tmp);
-		psidid = rb_entry(tmp, struct cifs_sid_id, rbnode);
-		if (nr_to_scan == 0 || *nr_del == nr_to_scan)
-			++(*nr_rem);
-		else {
-			if (time_after(jiffies, psidid->time + SID_MAP_EXPIRE)
-						&& psidid->refcount == 0) {
-				rb_erase(tmp, root);
-				++(*nr_del);
-			} else
-				++(*nr_rem);
-		}
-	}
-}
-
-/*
- * Run idmap cache shrinker.
- */
-static int
-cifs_idmap_shrinker(struct shrinker *shrink, struct shrink_control *sc)
-{
-	int nr_to_scan = sc->nr_to_scan;
-	int nr_del = 0;
-	int nr_rem = 0;
-	struct rb_root *root;
-
-	root = &uidtree;
-	spin_lock(&siduidlock);
-	shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
-	spin_unlock(&siduidlock);
-
-	root = &gidtree;
-	spin_lock(&sidgidlock);
-	shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
-	spin_unlock(&sidgidlock);
-
-	root = &siduidtree;
-	spin_lock(&uidsidlock);
-	shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
-	spin_unlock(&uidsidlock);
-
-	root = &sidgidtree;
-	spin_lock(&gidsidlock);
-	shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
-	spin_unlock(&gidsidlock);
-
-	return nr_rem;
-}
-
-static void
-sid_rb_insert(struct rb_root *root, unsigned long cid,
-		struct cifs_sid_id **psidid, char *typestr)
-{
-	char *strptr;
-	struct rb_node *node = root->rb_node;
-	struct rb_node *parent = NULL;
-	struct rb_node **linkto = &(root->rb_node);
-	struct cifs_sid_id *lsidid;
-
-	while (node) {
-		lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
-		parent = node;
-		if (cid > lsidid->id) {
-			linkto = &(node->rb_left);
-			node = node->rb_left;
-		}
-		if (cid < lsidid->id) {
-			linkto = &(node->rb_right);
-			node = node->rb_right;
-		}
-	}
-
-	(*psidid)->id = cid;
-	(*psidid)->time = jiffies - (SID_MAP_RETRY + 1);
-	(*psidid)->refcount = 0;
-
-	sprintf((*psidid)->sidstr, "%s", typestr);
-	strptr = (*psidid)->sidstr + strlen((*psidid)->sidstr);
-	sprintf(strptr, "%ld", cid);
-
-	clear_bit(SID_ID_PENDING, &(*psidid)->state);
-	clear_bit(SID_ID_MAPPED, &(*psidid)->state);
-
-	rb_link_node(&(*psidid)->rbnode, parent, linkto);
-	rb_insert_color(&(*psidid)->rbnode, root);
-}
-
-static struct cifs_sid_id *
-sid_rb_search(struct rb_root *root, unsigned long cid)
-{
-	struct rb_node *node = root->rb_node;
-	struct cifs_sid_id *lsidid;
-
-	while (node) {
-		lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
-		if (cid > lsidid->id)
-			node = node->rb_left;
-		else if (cid < lsidid->id)
-			node = node->rb_right;
-		else /* node found */
-			return lsidid;
-	}
-
-	return NULL;
-}
-
-static struct shrinker cifs_shrinker = {
-	.shrink = cifs_idmap_shrinker,
-	.seeks = DEFAULT_SEEKS,
-};
+static const struct cred *root_cred;
 
 static int
 cifs_idmap_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
 {
 	char *payload;
 
+	/*
+	 * If the payload is less than or equal to the size of a pointer, then
+	 * an allocation here is wasteful. Just copy the data directly to the
+	 * payload.value union member instead.
+	 *
+	 * With this however, you must check the datalen before trying to
+	 * dereference payload.data!
+	 */
+	if (prep->datalen <= sizeof(key->payload)) {
+		key->payload.value = 0;
+		memcpy(&key->payload.value, prep->data, prep->datalen);
+		key->datalen = prep->datalen;
+		return 0;
+	}
 	payload = kmalloc(prep->datalen, GFP_KERNEL);
 	if (!payload)
 		return -ENOMEM;
@@ -184,10 +76,11 @@ cifs_idmap_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
 static inline void
 cifs_idmap_key_destroy(struct key *key)
 {
-	kfree(key->payload.data);
+	if (key->datalen > sizeof(key->payload))
+		kfree(key->payload.data);
 }
 
-struct key_type cifs_idmap_key_type = {
+static struct key_type cifs_idmap_key_type = {
 	.name        = "cifs.idmap",
 	.instantiate = cifs_idmap_key_instantiate,
 	.destroy     = cifs_idmap_key_destroy,
@@ -195,221 +88,174 @@ struct key_type cifs_idmap_key_type = {
 	.match       = user_match,
 };
 
-static void
-sid_to_str(struct cifs_sid *sidptr, char *sidstr)
+static char *
+sid_to_key_str(struct cifs_sid *sidptr, unsigned int type)
 {
-	int i;
-	unsigned long saval;
-	char *strptr;
+	int i, len;
+	unsigned int saval;
+	char *sidstr, *strptr;
+	unsigned long long id_auth_val;
+
+	/* 3 bytes for prefix */
+	sidstr = kmalloc(3 + SID_STRING_BASE_SIZE +
+			 (SID_STRING_SUBAUTH_SIZE * sidptr->num_subauth),
+			 GFP_KERNEL);
+	if (!sidstr)
+		return sidstr;
 
 	strptr = sidstr;
+	len = sprintf(strptr, "%cs:S-%hhu", type == SIDOWNER ? 'o' : 'g',
+			sidptr->revision);
+	strptr += len;
+
+	/* The authority field is a single 48-bit number */
+	id_auth_val = (unsigned long long)sidptr->authority[5];
+	id_auth_val |= (unsigned long long)sidptr->authority[4] << 8;
+	id_auth_val |= (unsigned long long)sidptr->authority[3] << 16;
+	id_auth_val |= (unsigned long long)sidptr->authority[2] << 24;
+	id_auth_val |= (unsigned long long)sidptr->authority[1] << 32;
+	id_auth_val |= (unsigned long long)sidptr->authority[0] << 48;
 
-	sprintf(strptr, "%s", "S");
-	strptr = sidstr + strlen(sidstr);
-
-	sprintf(strptr, "-%d", sidptr->revision);
-	strptr = sidstr + strlen(sidstr);
+	/*
+	 * MS-DTYP states that if the authority is >= 2^32, then it should be
+	 * expressed as a hex value.
+	 */
+	if (id_auth_val <= UINT_MAX)
+		len = sprintf(strptr, "-%llu", id_auth_val);
+	else
+		len = sprintf(strptr, "-0x%llx", id_auth_val);
 
-	for (i = 0; i < 6; ++i) {
-		if (sidptr->authority[i]) {
-			sprintf(strptr, "-%d", sidptr->authority[i]);
-			strptr = sidstr + strlen(sidstr);
-		}
-	}
+	strptr += len;
 
 	for (i = 0; i < sidptr->num_subauth; ++i) {
 		saval = le32_to_cpu(sidptr->sub_auth[i]);
-		sprintf(strptr, "-%ld", saval);
-		strptr = sidstr + strlen(sidstr);
+		len = sprintf(strptr, "-%u", saval);
+		strptr += len;
 	}
-}
 
-static void
-cifs_copy_sid(struct cifs_sid *dst, const struct cifs_sid *src)
-{
-	memcpy(dst, src, sizeof(*dst));
-	dst->num_subauth = min_t(u8, src->num_subauth, NUM_SUBAUTHS);
+	return sidstr;
 }
 
-static void
-id_rb_insert(struct rb_root *root, struct cifs_sid *sidptr,
-		struct cifs_sid_id **psidid, char *typestr)
+/*
+ * if the two SIDs (roughly equivalent to a UUID for a user or group) are
+ * the same returns zero, if they do not match returns non-zero.
+ */
+static int
+compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
 {
-	int rc;
-	char *strptr;
-	struct rb_node *node = root->rb_node;
-	struct rb_node *parent = NULL;
-	struct rb_node **linkto = &(root->rb_node);
-	struct cifs_sid_id *lsidid;
-
-	while (node) {
-		lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
-		parent = node;
-		rc = compare_sids(sidptr, &((lsidid)->sid));
-		if (rc > 0) {
-			linkto = &(node->rb_left);
-			node = node->rb_left;
-		} else if (rc < 0) {
-			linkto = &(node->rb_right);
-			node = node->rb_right;
-		}
-	}
-
-	cifs_copy_sid(&(*psidid)->sid, sidptr);
-	(*psidid)->time = jiffies - (SID_MAP_RETRY + 1);
-	(*psidid)->refcount = 0;
+	int i;
+	int num_subauth, num_sat, num_saw;
 
-	sprintf((*psidid)->sidstr, "%s", typestr);
-	strptr = (*psidid)->sidstr + strlen((*psidid)->sidstr);
-	sid_to_str(&(*psidid)->sid, strptr);
+	if ((!ctsid) || (!cwsid))
+		return 1;
 
-	clear_bit(SID_ID_PENDING, &(*psidid)->state);
-	clear_bit(SID_ID_MAPPED, &(*psidid)->state);
+	/* compare the revision */
+	if (ctsid->revision != cwsid->revision) {
+		if (ctsid->revision > cwsid->revision)
+			return 1;
+		else
+			return -1;
+	}
 
-	rb_link_node(&(*psidid)->rbnode, parent, linkto);
-	rb_insert_color(&(*psidid)->rbnode, root);
-}
+	/* compare all of the six auth values */
+	for (i = 0; i < NUM_AUTHS; ++i) {
+		if (ctsid->authority[i] != cwsid->authority[i]) {
+			if (ctsid->authority[i] > cwsid->authority[i])
+				return 1;
+			else
+				return -1;
+		}
+	}
 
-static struct cifs_sid_id *
-id_rb_search(struct rb_root *root, struct cifs_sid *sidptr)
-{
-	int rc;
-	struct rb_node *node = root->rb_node;
-	struct cifs_sid_id *lsidid;
-
-	while (node) {
-		lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
-		rc = compare_sids(sidptr, &((lsidid)->sid));
-		if (rc > 0) {
-			node = node->rb_left;
-		} else if (rc < 0) {
-			node = node->rb_right;
-		} else /* node found */
-			return lsidid;
+	/* compare all of the subauth values if any */
+	num_sat = ctsid->num_subauth;
+	num_saw = cwsid->num_subauth;
+	num_subauth = num_sat < num_saw ? num_sat : num_saw;
+	if (num_subauth) {
+		for (i = 0; i < num_subauth; ++i) {
+			if (ctsid->sub_auth[i] != cwsid->sub_auth[i]) {
+				if (le32_to_cpu(ctsid->sub_auth[i]) >
+					le32_to_cpu(cwsid->sub_auth[i]))
+					return 1;
+				else
+					return -1;
+			}
+		}
 	}
 
-	return NULL;
+	return 0; /* sids compare/match */
 }
 
-static int
-sidid_pending_wait(void *unused)
+static void
+cifs_copy_sid(struct cifs_sid *dst, const struct cifs_sid *src)
 {
-	schedule();
-	return signal_pending(current) ? -ERESTARTSYS : 0;
+	int i;
+
+	dst->revision = src->revision;
+	dst->num_subauth = min_t(u8, src->num_subauth, SID_MAX_SUB_AUTHORITIES);
+	for (i = 0; i < NUM_AUTHS; ++i)
+		dst->authority[i] = src->authority[i];
+	for (i = 0; i < dst->num_subauth; ++i)
+		dst->sub_auth[i] = src->sub_auth[i];
 }
 
 static int
-id_to_sid(unsigned long cid, uint sidtype, struct cifs_sid *ssid)
+id_to_sid(unsigned int cid, uint sidtype, struct cifs_sid *ssid)
 {
-	int rc = 0;
+	int rc;
 	struct key *sidkey;
+	struct cifs_sid *ksid;
+	unsigned int ksid_size;
+	char desc[3 + 10 + 1]; /* 3 byte prefix + 10 bytes for value + NULL */
 	const struct cred *saved_cred;
-	struct cifs_sid *lsid;
-	struct cifs_sid_id *psidid, *npsidid;
-	struct rb_root *cidtree;
-	spinlock_t *cidlock;
-
-	if (sidtype == SIDOWNER) {
-		cidlock = &siduidlock;
-		cidtree = &uidtree;
-	} else if (sidtype == SIDGROUP) {
-		cidlock = &sidgidlock;
-		cidtree = &gidtree;
-	} else
-		return -EINVAL;
 
-	spin_lock(cidlock);
-	psidid = sid_rb_search(cidtree, cid);
-
-	if (!psidid) { /* node does not exist, allocate one & attempt adding */
-		spin_unlock(cidlock);
-		npsidid = kzalloc(sizeof(struct cifs_sid_id), GFP_KERNEL);
-		if (!npsidid)
-			return -ENOMEM;
-
-		npsidid->sidstr = kmalloc(SIDLEN, GFP_KERNEL);
-		if (!npsidid->sidstr) {
-			kfree(npsidid);
-			return -ENOMEM;
-		}
+	rc = snprintf(desc, sizeof(desc), "%ci:%u",
+			sidtype == SIDOWNER ? 'o' : 'g', cid);
+	if (rc >= sizeof(desc))
+		return -EINVAL;
 
-		spin_lock(cidlock);
-		psidid = sid_rb_search(cidtree, cid);
-		if (psidid) { /* node happened to get inserted meanwhile */
-			++psidid->refcount;
-			spin_unlock(cidlock);
-			kfree(npsidid->sidstr);
-			kfree(npsidid);
-		} else {
-			psidid = npsidid;
-			sid_rb_insert(cidtree, cid, &psidid,
-					sidtype == SIDOWNER ? "oi:" : "gi:");
-			++psidid->refcount;
-			spin_unlock(cidlock);
-		}
-	} else {
-		++psidid->refcount;
-		spin_unlock(cidlock);
+	rc = 0;
+	saved_cred = override_creds(root_cred);
+	sidkey = request_key(&cifs_idmap_key_type, desc, "");
+	if (IS_ERR(sidkey)) {
+		rc = -EINVAL;
+		cFYI(1, "%s: Can't map %cid %u to a SID", __func__,
+			sidtype == SIDOWNER ? 'u' : 'g', cid);
+		goto out_revert_creds;
+	} else if (sidkey->datalen < CIFS_SID_BASE_SIZE) {
+		rc = -EIO;
+		cFYI(1, "%s: Downcall contained malformed key "
+			"(datalen=%hu)", __func__, sidkey->datalen);
+		goto invalidate_key;
 	}
 
 	/*
-	 * If we are here, it is safe to access psidid and its fields
-	 * since a reference was taken earlier while holding the spinlock.
-	 * A reference on the node is put without holding the spinlock
-	 * and it is OK to do so in this case, shrinker will not erase
-	 * this node until all references are put and we do not access
-	 * any fields of the node after a reference is put .
+	 * A sid is usually too large to be embedded in payload.value, but if
+	 * there are no subauthorities and the host has 8-byte pointers, then
+	 * it could be.
 	 */
-	if (test_bit(SID_ID_MAPPED, &psidid->state)) {
-		cifs_copy_sid(ssid, &psidid->sid);
-		psidid->time = jiffies; /* update ts for accessing */
-		goto id_sid_out;
-	}
-
-	if (time_after(psidid->time + SID_MAP_RETRY, jiffies)) {
-		rc = -EINVAL;
-		goto id_sid_out;
+	ksid = sidkey->datalen <= sizeof(sidkey->payload) ?
+		(struct cifs_sid *)&sidkey->payload.value :
+		(struct cifs_sid *)sidkey->payload.data;
+
+	ksid_size = CIFS_SID_BASE_SIZE + (ksid->num_subauth * sizeof(__le32));
+	if (ksid_size > sidkey->datalen) {
+		rc = -EIO;
+		cFYI(1, "%s: Downcall contained malformed key (datalen=%hu, "
+			"ksid_size=%u)", __func__, sidkey->datalen, ksid_size);
+		goto invalidate_key;
 	}
 
-	if (!test_and_set_bit(SID_ID_PENDING, &psidid->state)) {
-		saved_cred = override_creds(root_cred);
-		sidkey = request_key(&cifs_idmap_key_type, psidid->sidstr, "");
-		if (IS_ERR(sidkey)) {
-			rc = -EINVAL;
-			cFYI(1, "%s: Can't map and id to a SID", __func__);
-		} else if (sidkey->datalen < sizeof(struct cifs_sid)) {
-			rc = -EIO;
-			cFYI(1, "%s: Downcall contained malformed key "
-				"(datalen=%hu)", __func__, sidkey->datalen);
-		} else {
-			lsid = (struct cifs_sid *)sidkey->payload.data;
-			cifs_copy_sid(&psidid->sid, lsid);
-			cifs_copy_sid(ssid, &psidid->sid);
-			set_bit(SID_ID_MAPPED, &psidid->state);
-			key_put(sidkey);
-			kfree(psidid->sidstr);
-		}
-		psidid->time = jiffies; /* update ts for accessing */
-		revert_creds(saved_cred);
-		clear_bit(SID_ID_PENDING, &psidid->state);
-		wake_up_bit(&psidid->state, SID_ID_PENDING);
-	} else {
-		rc = wait_on_bit(&psidid->state, SID_ID_PENDING,
-				sidid_pending_wait, TASK_INTERRUPTIBLE);
-		if (rc) {
-			cFYI(1, "%s: sidid_pending_wait interrupted %d",
-					__func__, rc);
-			--psidid->refcount;
-			return rc;
-		}
-		if (test_bit(SID_ID_MAPPED, &psidid->state))
-			cifs_copy_sid(ssid, &psidid->sid);
-		else
-			rc = -EINVAL;
-	}
-id_sid_out:
-	--psidid->refcount;
+	cifs_copy_sid(ssid, ksid);
+out_key_put:
+	key_put(sidkey);
+out_revert_creds:
+	revert_creds(saved_cred);
 	return rc;
+
+invalidate_key:
+	key_invalidate(sidkey);
+	goto out_key_put;
 }
 
 static int
@@ -417,111 +263,67 @@ sid_to_id(struct cifs_sb_info *cifs_sb, struct cifs_sid *psid,
 		struct cifs_fattr *fattr, uint sidtype)
 {
 	int rc;
-	unsigned long cid;
-	struct key *idkey;
+	struct key *sidkey;
+	char *sidstr;
 	const struct cred *saved_cred;
-	struct cifs_sid_id *psidid, *npsidid;
-	struct rb_root *cidtree;
-	spinlock_t *cidlock;
-
-	if (sidtype == SIDOWNER) {
-		cid = cifs_sb->mnt_uid; /* default uid, in case upcall fails */
-		cidlock = &siduidlock;
-		cidtree = &uidtree;
-	} else if (sidtype == SIDGROUP) {
-		cid = cifs_sb->mnt_gid; /* default gid, in case upcall fails */
-		cidlock = &sidgidlock;
-		cidtree = &gidtree;
-	} else
-		return -ENOENT;
-
-	spin_lock(cidlock);
-	psidid = id_rb_search(cidtree, psid);
-
-	if (!psidid) { /* node does not exist, allocate one & attempt adding */
-		spin_unlock(cidlock);
-		npsidid = kzalloc(sizeof(struct cifs_sid_id), GFP_KERNEL);
-		if (!npsidid)
-			return -ENOMEM;
-
-		npsidid->sidstr = kmalloc(SIDLEN, GFP_KERNEL);
-		if (!npsidid->sidstr) {
-			kfree(npsidid);
-			return -ENOMEM;
-		}
-
-		spin_lock(cidlock);
-		psidid = id_rb_search(cidtree, psid);
-		if (psidid) { /* node happened to get inserted meanwhile */
-			++psidid->refcount;
-			spin_unlock(cidlock);
-			kfree(npsidid->sidstr);
-			kfree(npsidid);
-		} else {
-			psidid = npsidid;
-			id_rb_insert(cidtree, psid, &psidid,
-					sidtype == SIDOWNER ? "os:" : "gs:");
-			++psidid->refcount;
-			spin_unlock(cidlock);
-		}
-	} else {
-		++psidid->refcount;
-		spin_unlock(cidlock);
-	}
+	uid_t fuid = cifs_sb->mnt_uid;
+	gid_t fgid = cifs_sb->mnt_gid;
 
 	/*
-	 * If we are here, it is safe to access psidid and its fields
-	 * since a reference was taken earlier while holding the spinlock.
-	 * A reference on the node is put without holding the spinlock
-	 * and it is OK to do so in this case, shrinker will not erase
-	 * this node until all references are put and we do not access
-	 * any fields of the node after a reference is put .
+	 * If we have too many subauthorities, then something is really wrong.
+	 * Just return an error.
 	 */
-	if (test_bit(SID_ID_MAPPED, &psidid->state)) {
-		cid = psidid->id;
-		psidid->time = jiffies; /* update ts for accessing */
-		goto sid_to_id_out;
+	if (unlikely(psid->num_subauth > SID_MAX_SUB_AUTHORITIES)) {
+		cFYI(1, "%s: %u subauthorities is too many!", __func__,
+			psid->num_subauth);
+		return -EIO;
 	}
 
-	if (time_after(psidid->time + SID_MAP_RETRY, jiffies))
-		goto sid_to_id_out;
-
-	if (!test_and_set_bit(SID_ID_PENDING, &psidid->state)) {
-		saved_cred = override_creds(root_cred);
-		idkey = request_key(&cifs_idmap_key_type, psidid->sidstr, "");
-		if (IS_ERR(idkey))
-			cFYI(1, "%s: Can't map SID to an id", __func__);
-		else {
-			cid = *(unsigned long *)idkey->payload.value;
-			psidid->id = cid;
-			set_bit(SID_ID_MAPPED, &psidid->state);
-			key_put(idkey);
-			kfree(psidid->sidstr);
-		}
-		revert_creds(saved_cred);
-		psidid->time = jiffies; /* update ts for accessing */
-		clear_bit(SID_ID_PENDING, &psidid->state);
-		wake_up_bit(&psidid->state, SID_ID_PENDING);
-	} else {
-		rc = wait_on_bit(&psidid->state, SID_ID_PENDING,
-				sidid_pending_wait, TASK_INTERRUPTIBLE);
-		if (rc) {
-			cFYI(1, "%s: sidid_pending_wait interrupted %d",
-					__func__, rc);
-			--psidid->refcount; /* decremented without spinlock */
-			return rc;
-		}
-		if (test_bit(SID_ID_MAPPED, &psidid->state))
-			cid = psidid->id;
+	sidstr = sid_to_key_str(psid, sidtype);
+	if (!sidstr)
+		return -ENOMEM;
+
+	saved_cred = override_creds(root_cred);
+	sidkey = request_key(&cifs_idmap_key_type, sidstr, "");
+	if (IS_ERR(sidkey)) {
+		rc = -EINVAL;
+		cFYI(1, "%s: Can't map SID %s to a %cid", __func__, sidstr,
+			sidtype == SIDOWNER ? 'u' : 'g');
+		goto out_revert_creds;
+	}
+
+	/*
+	 * FIXME: Here we assume that uid_t and gid_t are same size. It's
+	 * probably a safe assumption but might be better to check based on
+	 * sidtype.
+	 */
+	if (sidkey->datalen != sizeof(uid_t)) {
+		rc = -EIO;
+		cFYI(1, "%s: Downcall contained malformed key "
+			"(datalen=%hu)", __func__, sidkey->datalen);
+		key_invalidate(sidkey);
+		goto out_key_put;
 	}
 
-sid_to_id_out:
-	--psidid->refcount; /* decremented without spinlock */
 	if (sidtype == SIDOWNER)
-		fattr->cf_uid = cid;
+		memcpy(&fuid, &sidkey->payload.value, sizeof(uid_t));
 	else
-		fattr->cf_gid = cid;
+		memcpy(&fgid, &sidkey->payload.value, sizeof(gid_t));
+
+out_key_put:
+	key_put(sidkey);
+out_revert_creds:
+	revert_creds(saved_cred);
+	kfree(sidstr);
 
+	/*
+	 * Note that we return 0 here unconditionally. If the mapping
+	 * fails then we just fall back to using the mnt_uid/mnt_gid.
+	 */
+	if (sidtype == SIDOWNER)
+		fattr->cf_uid = fuid;
+	else
+		fattr->cf_gid = fgid;
 	return 0;
 }
 
@@ -544,19 +346,15 @@ init_cifs_idmap(void)
 	if (!cred)
 		return -ENOMEM;
 
-	keyring = key_alloc(&key_type_keyring, ".cifs_idmap", 0, 0, cred,
-			    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
-			    KEY_USR_VIEW | KEY_USR_READ,
-			    KEY_ALLOC_NOT_IN_QUOTA);
+	keyring = keyring_alloc(".cifs_idmap", 0, 0, cred,
+				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				KEY_USR_VIEW | KEY_USR_READ,
+				KEY_ALLOC_NOT_IN_QUOTA, NULL);
 	if (IS_ERR(keyring)) {
 		ret = PTR_ERR(keyring);
 		goto failed_put_cred;
 	}
 
-	ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
-	if (ret < 0)
-		goto failed_put_key;
-
 	ret = register_key_type(&cifs_idmap_key_type);
 	if (ret < 0)
 		goto failed_put_key;
@@ -568,17 +366,6 @@ init_cifs_idmap(void)
 	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 	root_cred = cred;
 
-	spin_lock_init(&siduidlock);
-	uidtree = RB_ROOT;
-	spin_lock_init(&sidgidlock);
-	gidtree = RB_ROOT;
-
-	spin_lock_init(&uidsidlock);
-	siduidtree = RB_ROOT;
-	spin_lock_init(&gidsidlock);
-	sidgidtree = RB_ROOT;
-	register_shrinker(&cifs_shrinker);
-
 	cFYI(1, "cifs idmap keyring: %d", key_serial(keyring));
 	return 0;
 
@@ -595,89 +382,9 @@ exit_cifs_idmap(void)
 	key_revoke(root_cred->thread_keyring);
 	unregister_key_type(&cifs_idmap_key_type);
 	put_cred(root_cred);
-	unregister_shrinker(&cifs_shrinker);
 	cFYI(1, "Unregistered %s key type", cifs_idmap_key_type.name);
 }
 
-void
-cifs_destroy_idmaptrees(void)
-{
-	struct rb_root *root;
-	struct rb_node *node;
-
-	root = &uidtree;
-	spin_lock(&siduidlock);
-	while ((node = rb_first(root)))
-		rb_erase(node, root);
-	spin_unlock(&siduidlock);
-
-	root = &gidtree;
-	spin_lock(&sidgidlock);
-	while ((node = rb_first(root)))
-		rb_erase(node, root);
-	spin_unlock(&sidgidlock);
-
-	root = &siduidtree;
-	spin_lock(&uidsidlock);
-	while ((node = rb_first(root)))
-		rb_erase(node, root);
-	spin_unlock(&uidsidlock);
-
-	root = &sidgidtree;
-	spin_lock(&gidsidlock);
-	while ((node = rb_first(root)))
-		rb_erase(node, root);
-	spin_unlock(&gidsidlock);
-}
-
-/* if the two SIDs (roughly equivalent to a UUID for a user or group) are
-   the same returns 1, if they do not match returns 0 */
-int compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
-{
-	int i;
-	int num_subauth, num_sat, num_saw;
-
-	if ((!ctsid) || (!cwsid))
-		return 1;
-
-	/* compare the revision */
-	if (ctsid->revision != cwsid->revision) {
-		if (ctsid->revision > cwsid->revision)
-			return 1;
-		else
-			return -1;
-	}
-
-	/* compare all of the six auth values */
-	for (i = 0; i < 6; ++i) {
-		if (ctsid->authority[i] != cwsid->authority[i]) {
-			if (ctsid->authority[i] > cwsid->authority[i])
-				return 1;
-			else
-				return -1;
-		}
-	}
-
-	/* compare all of the subauth values if any */
-	num_sat = ctsid->num_subauth;
-	num_saw = cwsid->num_subauth;
-	num_subauth = num_sat < num_saw ? num_sat : num_saw;
-	if (num_subauth) {
-		for (i = 0; i < num_subauth; ++i) {
-			if (ctsid->sub_auth[i] != cwsid->sub_auth[i]) {
-				if (le32_to_cpu(ctsid->sub_auth[i]) >
-					le32_to_cpu(cwsid->sub_auth[i]))
-					return 1;
-				else
-					return -1;
-			}
-		}
-	}
-
-	return 0; /* sids compare/match */
-}
-
-
 /* copy ntsd, owner sid, and group sid from a security descriptor to another */
 static void copy_sec_desc(const struct cifs_ntsd *pntsd,
 				struct cifs_ntsd *pnntsd, __u32 sidsoffset)
@@ -811,7 +518,7 @@ static __u16 fill_ace_for_sid(struct cifs_ace *pntace,
 
 	pntace->sid.revision = psid->revision;
 	pntace->sid.num_subauth = psid->num_subauth;
-	for (i = 0; i < 6; i++)
+	for (i = 0; i < NUM_AUTHS; i++)
 		pntace->sid.authority[i] = psid->authority[i];
 	for (i = 0; i < psid->num_subauth; i++)
 		pntace->sid.sub_auth[i] = psid->sub_auth[i];
@@ -987,8 +694,8 @@ static int parse_sid(struct cifs_sid *psid, char *end_of_acl)
 		return -EINVAL;
 	}
 
-	if (psid->num_subauth) {
 #ifdef CONFIG_CIFS_DEBUG2
+	if (psid->num_subauth) {
 		int i;
 		cFYI(1, "SID revision %d num_auth %d",
 			psid->revision, psid->num_subauth);
@@ -1002,8 +709,8 @@ static int parse_sid(struct cifs_sid *psid, char *end_of_acl)
 			num auths and therefore go off the end */
 		cFYI(1, "RID 0x%x",
 			le32_to_cpu(psid->sub_auth[psid->num_subauth-1]));
-#endif
 	}
+#endif
 
 	return 0;
 }
@@ -1307,42 +1014,39 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 nmode,
 
 	/* Get the security descriptor */
 	pntsd = get_cifs_acl(CIFS_SB(inode->i_sb), inode, path, &secdesclen);
-
-	/* Add three ACEs for owner, group, everyone getting rid of
-	   other ACEs as chmod disables ACEs and set the security descriptor */
-
 	if (IS_ERR(pntsd)) {
 		rc = PTR_ERR(pntsd);
 		cERROR(1, "%s: error %d getting sec desc", __func__, rc);
-	} else {
-		/* allocate memory for the smb header,
-		   set security descriptor request security descriptor
-		   parameters, and secuirty descriptor itself */
-
-		secdesclen = secdesclen < DEFSECDESCLEN ?
-					DEFSECDESCLEN : secdesclen;
-		pnntsd = kmalloc(secdesclen, GFP_KERNEL);
-		if (!pnntsd) {
-			cERROR(1, "Unable to allocate security descriptor");
-			kfree(pntsd);
-			return -ENOMEM;
-		}
+		goto out;
+	}
 
-		rc = build_sec_desc(pntsd, pnntsd, secdesclen, nmode, uid, gid,
-					&aclflag);
+	/*
+	 * Add three ACEs for owner, group, everyone getting rid of other ACEs
+	 * as chmod disables ACEs and set the security descriptor. Allocate
+	 * memory for the smb header, set security descriptor request security
+	 * descriptor parameters, and secuirty descriptor itself
+	 */
+	secdesclen = max_t(u32, secdesclen, DEFAULT_SEC_DESC_LEN);
+	pnntsd = kmalloc(secdesclen, GFP_KERNEL);
+	if (!pnntsd) {
+		cERROR(1, "Unable to allocate security descriptor");
+		kfree(pntsd);
+		return -ENOMEM;
+	}
 
-		cFYI(DBG2, "build_sec_desc rc: %d", rc);
+	rc = build_sec_desc(pntsd, pnntsd, secdesclen, nmode, uid, gid,
+				&aclflag);
 
-		if (!rc) {
-			/* Set the security descriptor */
-			rc = set_cifs_acl(pnntsd, secdesclen, inode,
-						path, aclflag);
-			cFYI(DBG2, "set_cifs_acl rc: %d", rc);
-		}
+	cFYI(DBG2, "build_sec_desc rc: %d", rc);
 
-		kfree(pnntsd);
-		kfree(pntsd);
+	if (!rc) {
+		/* Set the security descriptor */
+		rc = set_cifs_acl(pnntsd, secdesclen, inode, path, aclflag);
+		cFYI(DBG2, "set_cifs_acl rc: %d", rc);
 	}
 
+	kfree(pnntsd);
+	kfree(pntsd);
+out:
 	return rc;
 }