linux-kernel - [PATCH 10/12] cachefiles: Set object to close if ondemand

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Date: Wed, 24 Apr 2024 11:39:14 +0800
From: libaokun@...weicloud.com
To: netfs@...ts.linux.dev
Cc: dhowells@...hat.com,
	jlayton@...nel.org,
	zhujia.zj@...edance.com,
	jefflexu@...ux.alibaba.com,
	linux-erofs@...ts.ozlabs.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	libaokun@...weicloud.com,
	Zizhi Wo <wozizhi@...wei.com>,
	Baokun Li <libaokun1@...wei.com>
Subject: [PATCH 10/12] cachefiles: Set object to close if ondemand_id < 0 in copen

From: Zizhi Wo <wozizhi@...wei.com>

If copen is maliciously called in the user mode, it may delete the request
corresponding to the random id. And the request may have not been read yet.

Note that when the object is set to reopen, the open request will be done
with the still reopen state in above case. As a result, the request
corresponding to this object is always skipped in select_req function, so
the read request is never completed and blocks other process.

Fix this issue by simply set object to close if its id < 0 in copen.

Signed-off-by: Zizhi Wo <wozizhi@...wei.com>
Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
 fs/cachefiles/ondemand.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 7c2d43104120..673e7ad52041 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -182,6 +182,7 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 	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) {
@@ -201,7 +202,6 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 		goto out;
 	}
 
-	info = req->object->ondemand;
 	spin_lock(&info->lock);
 	/* The anonymous fd was closed before copen ? */
 	if (info->ondemand_id == CACHEFILES_ONDEMAND_ID_CLOSED) {
@@ -222,6 +222,11 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 	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;
 }
-- 
2.39.2