6.6-stable review patch. If anyone has any objections, please let me know.
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From: Baokun Li libaokun1@huawei.com
[ Upstream commit 4b4391e77a6bf24cba2ef1590e113d9b73b11039 ]
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 during colse fd, so this may cause a cache UAF.
So grab the cache reference count before fd_install(). In addition, by kernel convention, fd is taken over by the user land after fd_install(), and the kernel should not call close_fd() after that, i.e., it should call fd_install() after everything is ready, thus fd_install() is called after copy_to_user() succeeds.
Fixes: c8383054506c ("cachefiles: notify the user daemon when looking up cookie") Suggested-by: Hou Tao houtao1@huawei.com Signed-off-by: Baokun Li libaokun1@huawei.com Link: https://lore.kernel.org/r/20240522114308.2402121-10-libaokun@huaweicloud.com Acked-by: Jeff Layton jlayton@kernel.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/cachefiles/ondemand.c | 53 +++++++++++++++++++++++++--------------- 1 file changed, 33 insertions(+), 20 deletions(-)
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index 773c3b407a33b..a8cfa5047aaf8 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -4,6 +4,11 @@ #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)) @@ -250,14 +255,14 @@ 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); @@ -269,16 +274,16 @@ 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; }
@@ -286,16 +291,15 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) if (object->ondemand->ondemand_id > 0) { spin_unlock(&object->ondemand->lock); /* Pair with check in cachefiles_ondemand_fd_release(). */ - file->private_data = NULL; + anon_file->file->private_data = NULL; ret = -EEXIST; 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->ondemand->ondemand_id = object_id; spin_unlock(&object->ondemand->lock);
@@ -304,9 +308,11 @@ 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_erase(&cache->ondemand_ids, object_id); err: @@ -363,6 +369,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, struct cachefiles_msg *msg; 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); @@ -396,7 +403,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, xa_unlock(&cache->reqs);
if (msg->opcode == CACHEFILES_OP_OPEN) { - ret = cachefiles_ondemand_get_fd(req); + ret = cachefiles_ondemand_get_fd(req, &anon_file); if (ret) goto out; } @@ -404,10 +411,16 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, 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; - if (msg->opcode == CACHEFILES_OP_OPEN) - close_fd(((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: cachefiles_put_object(req->object, cachefiles_obj_put_read_req);