1 files changed, 208 insertions, 62 deletions

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 4ba42f1fa3..470c966583 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -1,22 +1,42 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
-#include <linux/fdtable.h>
 #include <linux/anon_inodes.h>
 #include <linux/uio.h>
 #include "internal.h"
 
+struct ondemand_anon_file {
+	struct file *file;
+	int fd;
+};
+
+static inline void cachefiles_req_put(struct cachefiles_req *req)
+{
+	if (refcount_dec_and_test(&req->ref))
+		kfree(req);
+}
+
 static int cachefiles_ondemand_fd_release(struct inode *inode,
 					  struct file *file)
 {
 	struct cachefiles_object *object = file->private_data;
-	struct cachefiles_cache *cache = object->volume->cache;
-	struct cachefiles_ondemand_info *info = object->ondemand;
-	int object_id = info->ondemand_id;
+	struct cachefiles_cache *cache;
+	struct cachefiles_ondemand_info *info;
+	int object_id;
 	struct cachefiles_req *req;
-	XA_STATE(xas, &cache->reqs, 0);
+	XA_STATE(xas, NULL, 0);
+
+	if (!object)
+		return 0;
+
+	info = object->ondemand;
+	cache = object->volume->cache;
+	xas.xa = &cache->reqs;
 
 	xa_lock(&cache->reqs);
+	spin_lock(&info->lock);
+	object_id = info->ondemand_id;
 	info->ondemand_id = CACHEFILES_ONDEMAND_ID_CLOSED;
 	cachefiles_ondemand_set_object_close(object);
+	spin_unlock(&info->lock);
 
 	/* Only flush CACHEFILES_REQ_NEW marked req to avoid race with daemon_read */
 	xas_for_each_marked(&xas, req, ULONG_MAX, CACHEFILES_REQ_NEW) {
@@ -76,12 +96,12 @@ static loff_t cachefiles_ondemand_fd_llseek(struct file *filp, loff_t pos,
 }
 
 static long cachefiles_ondemand_fd_ioctl(struct file *filp, unsigned int ioctl,
-					 unsigned long arg)
+					 unsigned long id)
 {
 	struct cachefiles_object *object = filp->private_data;
 	struct cachefiles_cache *cache = object->volume->cache;
 	struct cachefiles_req *req;
-	unsigned long id;
+	XA_STATE(xas, &cache->reqs, id);
 
 	if (ioctl != CACHEFILES_IOC_READ_COMPLETE)
 		return -EINVAL;
@@ -89,10 +109,15 @@ static long cachefiles_ondemand_fd_ioctl(struct file *filp, unsigned int ioctl,
 	if (!test_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags))
 		return -EOPNOTSUPP;
 
-	id = arg;
-	req = xa_erase(&cache->reqs, id);
-	if (!req)
+	xa_lock(&cache->reqs);
+	req = xas_load(&xas);
+	if (!req || req->msg.opcode != CACHEFILES_OP_READ ||
+	    req->object != object) {
+		xa_unlock(&cache->reqs);
 		return -EINVAL;
+	}
+	xas_store(&xas, NULL);
+	xa_unlock(&cache->reqs);
 
 	trace_cachefiles_ondemand_cread(object, id);
 	complete(&req->done);
@@ -116,10 +141,12 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 {
 	struct cachefiles_req *req;
 	struct fscache_cookie *cookie;
+	struct cachefiles_ondemand_info *info;
 	char *pid, *psize;
 	unsigned long id;
 	long size;
 	int ret;
+	XA_STATE(xas, &cache->reqs, 0);
 
 	if (!test_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags))
 		return -EOPNOTSUPP;
@@ -143,10 +170,18 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 	if (ret)
 		return ret;
 
-	req = xa_erase(&cache->reqs, id);
-	if (!req)
+	xa_lock(&cache->reqs);
+	xas.xa_index = id;
+	req = xas_load(&xas);
+	if (!req || req->msg.opcode != CACHEFILES_OP_OPEN ||
+	    !req->object->ondemand->ondemand_id) {
+		xa_unlock(&cache->reqs);
 		return -EINVAL;
+	}
+	xas_store(&xas, NULL);
+	xa_unlock(&cache->reqs);
 
+	info = req->object->ondemand;
 	/* fail OPEN request if copen format is invalid */
 	ret = kstrtol(psize, 0, &size);
 	if (ret) {
@@ -166,6 +201,32 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 		goto out;
 	}
 
+	spin_lock(&info->lock);
+	/*
+	 * The anonymous fd was closed before copen ? Fail the request.
+	 *
+	 *             t1             |             t2
+	 * ---------------------------------------------------------
+	 *                             cachefiles_ondemand_copen
+	 *                             req = xa_erase(&cache->reqs, id)
+	 * // Anon fd is maliciously closed.
+	 * cachefiles_ondemand_fd_release
+	 * xa_lock(&cache->reqs)
+	 * cachefiles_ondemand_set_object_close(object)
+	 * xa_unlock(&cache->reqs)
+	 *                             cachefiles_ondemand_set_object_open
+	 *                             // No one will ever close it again.
+	 * cachefiles_ondemand_daemon_read
+	 * cachefiles_ondemand_select_req
+	 *
+	 * Get a read req but its fd is already closed. The daemon can't
+	 * issue a cread ioctl with an closed fd, then hung.
+	 */
+	if (info->ondemand_id == CACHEFILES_ONDEMAND_ID_CLOSED) {
+		spin_unlock(&info->lock);
+		req->error = -EBADFD;
+		goto out;
+	}
 	cookie = req->object->cookie;
 	cookie->object_size = size;
 	if (size)
@@ -175,9 +236,15 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 	trace_cachefiles_ondemand_copen(req->object, id, size);
 
 	cachefiles_ondemand_set_object_open(req->object);
+	spin_unlock(&info->lock);
 	wake_up_all(&cache->daemon_pollwq);
 
 out:
+	spin_lock(&info->lock);
+	/* Need to set object close to avoid reopen status continuing */
+	if (info->ondemand_id == CACHEFILES_ONDEMAND_ID_CLOSED)
+		cachefiles_ondemand_set_object_close(req->object);
+	spin_unlock(&info->lock);
 	complete(&req->done);
 	return ret;
 }
@@ -205,14 +272,14 @@ int cachefiles_ondemand_restore(struct cachefiles_cache *cache, char *args)
 	return 0;
 }
 
-static int cachefiles_ondemand_get_fd(struct cachefiles_req *req)
+static int cachefiles_ondemand_get_fd(struct cachefiles_req *req,
+				      struct ondemand_anon_file *anon_file)
 {
 	struct cachefiles_object *object;
 	struct cachefiles_cache *cache;
 	struct cachefiles_open *load;
-	struct file *file;
 	u32 object_id;
-	int ret, fd;
+	int ret;
 
 	object = cachefiles_grab_object(req->object,
 			cachefiles_obj_get_ondemand_fd);
@@ -224,35 +291,53 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req)
 	if (ret < 0)
 		goto err;
 
-	fd = get_unused_fd_flags(O_WRONLY);
-	if (fd < 0) {
-		ret = fd;
+	anon_file->fd = get_unused_fd_flags(O_WRONLY);
+	if (anon_file->fd < 0) {
+		ret = anon_file->fd;
 		goto err_free_id;
 	}
 
-	file = anon_inode_getfile("[cachefiles]", &cachefiles_ondemand_fd_fops,
-				  object, O_WRONLY);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
+	anon_file->file = anon_inode_getfile("[cachefiles]",
+				&cachefiles_ondemand_fd_fops, object, O_WRONLY);
+	if (IS_ERR(anon_file->file)) {
+		ret = PTR_ERR(anon_file->file);
 		goto err_put_fd;
 	}
 
-	file->f_mode |= FMODE_PWRITE | FMODE_LSEEK;
-	fd_install(fd, file);
+	spin_lock(&object->ondemand->lock);
+	if (object->ondemand->ondemand_id > 0) {
+		spin_unlock(&object->ondemand->lock);
+		/* Pair with check in cachefiles_ondemand_fd_release(). */
+		anon_file->file->private_data = NULL;
+		ret = -EEXIST;
+		goto err_put_file;
+	}
+
+	anon_file->file->f_mode |= FMODE_PWRITE | FMODE_LSEEK;
 
 	load = (void *)req->msg.data;
-	load->fd = fd;
+	load->fd = anon_file->fd;
 	object->ondemand->ondemand_id = object_id;
+	spin_unlock(&object->ondemand->lock);
 
 	cachefiles_get_unbind_pincount(cache);
 	trace_cachefiles_ondemand_open(object, &req->msg, load);
 	return 0;
 
+err_put_file:
+	fput(anon_file->file);
+	anon_file->file = NULL;
 err_put_fd:
-	put_unused_fd(fd);
+	put_unused_fd(anon_file->fd);
+	anon_file->fd = ret;
 err_free_id:
 	xa_erase(&cache->ondemand_ids, object_id);
 err:
+	spin_lock(&object->ondemand->lock);
+	/* Avoid marking an opened object as closed. */
+	if (object->ondemand->ondemand_id <= 0)
+		cachefiles_ondemand_set_object_close(object);
+	spin_unlock(&object->ondemand->lock);
 	cachefiles_put_object(object, cachefiles_obj_put_ondemand_fd);
 	return ret;
 }
@@ -294,14 +379,28 @@ static struct cachefiles_req *cachefiles_ondemand_select_req(struct xa_state *xa
 	return NULL;
 }
 
+static inline bool cachefiles_ondemand_finish_req(struct cachefiles_req *req,
+						  struct xa_state *xas, int err)
+{
+	if (unlikely(!xas || !req))
+		return false;
+
+	if (xa_cmpxchg(xas->xa, xas->xa_index, req, NULL, 0) != req)
+		return false;
+
+	req->error = err;
+	complete(&req->done);
+	return true;
+}
+
 ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
 					char __user *_buffer, size_t buflen)
 {
 	struct cachefiles_req *req;
 	struct cachefiles_msg *msg;
-	unsigned long id = 0;
 	size_t n;
 	int ret = 0;
+	struct ondemand_anon_file anon_file;
 	XA_STATE(xas, &cache->reqs, cache->req_id_next);
 
 	xa_lock(&cache->reqs);
@@ -330,42 +429,37 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
 
 	xas_clear_mark(&xas, CACHEFILES_REQ_NEW);
 	cache->req_id_next = xas.xa_index + 1;
+	refcount_inc(&req->ref);
+	cachefiles_grab_object(req->object, cachefiles_obj_get_read_req);
 	xa_unlock(&cache->reqs);
 
-	id = xas.xa_index;
-
 	if (msg->opcode == CACHEFILES_OP_OPEN) {
-		ret = cachefiles_ondemand_get_fd(req);
-		if (ret) {
-			cachefiles_ondemand_set_object_close(req->object);
-			goto error;
-		}
+		ret = cachefiles_ondemand_get_fd(req, &anon_file);
+		if (ret)
+			goto out;
 	}
 
-	msg->msg_id = id;
+	msg->msg_id = xas.xa_index;
 	msg->object_id = req->object->ondemand->ondemand_id;
 
-	if (copy_to_user(_buffer, msg, n) != 0) {
+	if (copy_to_user(_buffer, msg, n) != 0)
 		ret = -EFAULT;
-		goto err_put_fd;
-	}
 
-	/* CLOSE request has no reply */
-	if (msg->opcode == CACHEFILES_OP_CLOSE) {
-		xa_erase(&cache->reqs, id);
-		complete(&req->done);
+	if (msg->opcode == CACHEFILES_OP_OPEN) {
+		if (ret < 0) {
+			fput(anon_file.file);
+			put_unused_fd(anon_file.fd);
+			goto out;
+		}
+		fd_install(anon_file.fd, anon_file.file);
 	}
-
-	return n;
-
-err_put_fd:
-	if (msg->opcode == CACHEFILES_OP_OPEN)
-		close_fd(((struct cachefiles_open *)msg->data)->fd);
-error:
-	xa_erase(&cache->reqs, id);
-	req->error = ret;
-	complete(&req->done);
-	return ret;
+out:
+	cachefiles_put_object(req->object, cachefiles_obj_put_read_req);
+	/* Remove error request and CLOSE request has no reply */
+	if (ret || msg->opcode == CACHEFILES_OP_CLOSE)
+		cachefiles_ondemand_finish_req(req, &xas, ret);
+	cachefiles_req_put(req);
+	return ret ? ret : n;
 }
 
 typedef int (*init_req_fn)(struct cachefiles_req *req, void *private);
@@ -395,6 +489,7 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
 		goto out;
 	}
 
+	refcount_set(&req->ref, 1);
 	req->object = object;
 	init_completion(&req->done);
 	req->msg.opcode = opcode;
@@ -422,7 +517,8 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
 		 */
 		xas_lock(&xas);
 
-		if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
+		if (test_bit(CACHEFILES_DEAD, &cache->flags) ||
+		    cachefiles_ondemand_object_is_dropping(object)) {
 			xas_unlock(&xas);
 			ret = -EIO;
 			goto out;
@@ -432,20 +528,32 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
 		smp_mb();
 
 		if (opcode == CACHEFILES_OP_CLOSE &&
-			!cachefiles_ondemand_object_is_open(object)) {
+		    !cachefiles_ondemand_object_is_open(object)) {
 			WARN_ON_ONCE(object->ondemand->ondemand_id == 0);
 			xas_unlock(&xas);
 			ret = -EIO;
 			goto out;
 		}
 
-		xas.xa_index = 0;
+		/*
+		 * Cyclically find a free xas to avoid msg_id reuse that would
+		 * cause the daemon to successfully copen a stale msg_id.
+		 */
+		xas.xa_index = cache->msg_id_next;
 		xas_find_marked(&xas, UINT_MAX, XA_FREE_MARK);
+		if (xas.xa_node == XAS_RESTART) {
+			xas.xa_index = 0;
+			xas_find_marked(&xas, cache->msg_id_next - 1, XA_FREE_MARK);
+		}
 		if (xas.xa_node == XAS_RESTART)
 			xas_set_err(&xas, -EBUSY);
+
 		xas_store(&xas, req);
-		xas_clear_mark(&xas, XA_FREE_MARK);
-		xas_set_mark(&xas, CACHEFILES_REQ_NEW);
+		if (xas_valid(&xas)) {
+			cache->msg_id_next = xas.xa_index + 1;
+			xas_clear_mark(&xas, XA_FREE_MARK);
+			xas_set_mark(&xas, CACHEFILES_REQ_NEW);
+		}
 		xas_unlock(&xas);
 	} while (xas_nomem(&xas, GFP_KERNEL));
 
@@ -454,16 +562,27 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
 		goto out;
 
 	wake_up_all(&cache->daemon_pollwq);
-	wait_for_completion(&req->done);
-	ret = req->error;
-	kfree(req);
+wait:
+	ret = wait_for_completion_killable(&req->done);
+	if (!ret) {
+		ret = req->error;
+	} else {
+		ret = -EINTR;
+		if (!cachefiles_ondemand_finish_req(req, &xas, ret)) {
+			/* Someone will complete it soon. */
+			cpu_relax();
+			goto wait;
+		}
+	}
+	cachefiles_req_put(req);
 	return ret;
 out:
 	/* Reset the object to close state in error handling path.
 	 * If error occurs after creating the anonymous fd,
 	 * cachefiles_ondemand_fd_release() will set object to close.
 	 */
-	if (opcode == CACHEFILES_OP_OPEN)
+	if (opcode == CACHEFILES_OP_OPEN &&
+	    !cachefiles_ondemand_object_is_dropping(object))
 		cachefiles_ondemand_set_object_close(object);
 	kfree(req);
 	return ret;
@@ -562,8 +681,34 @@ int cachefiles_ondemand_init_object(struct cachefiles_object *object)
 
 void cachefiles_ondemand_clean_object(struct cachefiles_object *object)
 {
+	unsigned long index;
+	struct cachefiles_req *req;
+	struct cachefiles_cache *cache;
+
+	if (!object->ondemand)
+		return;
+
 	cachefiles_ondemand_send_req(object, CACHEFILES_OP_CLOSE, 0,
 			cachefiles_ondemand_init_close_req, NULL);
+
+	if (!object->ondemand->ondemand_id)
+		return;
+
+	/* Cancel all requests for the object that is being dropped. */
+	cache = object->volume->cache;
+	xa_lock(&cache->reqs);
+	cachefiles_ondemand_set_object_dropping(object);
+	xa_for_each(&cache->reqs, index, req) {
+		if (req->object == object) {
+			req->error = -EIO;
+			complete(&req->done);
+			__xa_erase(&cache->reqs, index);
+		}
+	}
+	xa_unlock(&cache->reqs);
+
+	/* Wait for ondemand_object_worker() to finish to avoid UAF. */
+	cancel_work_sync(&object->ondemand->ondemand_work);
 }
 
 int cachefiles_ondemand_init_obj_info(struct cachefiles_object *object,
@@ -578,6 +723,7 @@ int cachefiles_ondemand_init_obj_info(struct cachefiles_object *object,
 		return -ENOMEM;
 
 	object->ondemand->object = object;
+	spin_lock_init(&object->ondemand->lock);
 	INIT_WORK(&object->ondemand->ondemand_work, ondemand_object_worker);
 	return 0;
 }