hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB5UKT
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After installing the anonymous fd, we can now see it in userland and close it. However, at this point we may not have gotten the reference count of the cache, but we will put it in the close fd, so this may cause a cache UAF.
To avoid this, we will make the anonymous fd accessible to the userland by executing fd_install() after copy_to_user() has succeeded, and by this point we will have already grabbed the reference count of the cache.
Signed-off-by: Baokun Li libaokun1@huawei.com --- fs/cachefiles/ondemand.c | 54 ++++++++++++++++++++++++---------------- 1 file changed, 33 insertions(+), 21 deletions(-)
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index da5afd162f64..cf996eadd1af 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -6,6 +6,11 @@ #include <linux/module.h> #include "internal.h"
+struct anon_file { + struct file *file; + int fd; +}; + static bool cachefiles_buffered_ondemand = true; module_param_named(buffered_ondemand, cachefiles_buffered_ondemand, bool, 0644);
@@ -249,14 +254,14 @@ 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 anon_file *anon_file) { struct cachefiles_object *object = req->object; struct cachefiles_cache *cache; struct cachefiles_open *load; - struct file *file; u32 object_id; - int ret, fd; + int ret;
object->fscache.cache->ops->grab_object(&object->fscache, cachefiles_obj_get_ondemand_fd); @@ -273,16 +278,16 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) goto err; object_id = ret;
- 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; }
@@ -290,15 +295,14 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) if (object->private->ondemand_id > 0) { spin_unlock(&object->private->lock); ret = -EEXIST; - file->private_data = NULL; + anon_file->file->private_data = NULL; goto err_put_file; }
- file->f_mode |= FMODE_PWRITE | FMODE_LSEEK; - fd_install(fd, file); + anon_file->file->f_mode |= FMODE_PWRITE | FMODE_LSEEK;
load = (void *)req->msg.data; - load->fd = fd; + load->fd = anon_file->fd; object->private->ondemand_id = object_id; spin_unlock(&object->private->lock);
@@ -306,9 +310,11 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) return 0;
err_put_file: - fput(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_lock(&cache->ondemand_ids.idr_rt); idr_remove(&cache->ondemand_ids, object_id); @@ -377,6 +383,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, size_t n; int ret = 0; struct radix_tree_iter iter; + struct anon_file anon_file;
/* * Cyclically search for a request that has not ever been processed, @@ -410,7 +417,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, id = iter.index;
if (msg->opcode == CACHEFILES_OP_OPEN) { - ret = cachefiles_ondemand_get_fd(req); + ret = cachefiles_ondemand_get_fd(req, &anon_file); if (ret) goto out; } @@ -418,11 +425,16 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, msg->msg_id = id; msg->object_id = req->object->private->ondemand_id;
- if (copy_to_user(_buffer, msg, n) != 0) { + if (copy_to_user(_buffer, msg, n) != 0) ret = -EFAULT; - if (msg->opcode == CACHEFILES_OP_OPEN) - __close_fd(current->files, - ((struct cachefiles_open *)msg->data)->fd); + + 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); }
out: