Patch "cachefiles: Set object to close if ondemand_id < 0 in copen" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    cachefiles: Set object to close if ondemand_id < 0 in copen

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     cachefiles-set-object-to-close-if-ondemand_id-0-in-c.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7d4df3597d1e734fac356c90891819ee386ff8de
Author: Zizhi Wo <wozizhi@xxxxxxxxxx>
Date:   Wed May 22 19:43:06 2024 +0800

    cachefiles: Set object to close if ondemand_id < 0 in copen
    
    [ Upstream commit 4f8703fb3482f92edcfd31661857b16fec89c2c0 ]
    
    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@xxxxxxxxxx>
    Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240522114308.2402121-11-libaokun@xxxxxxxxxxxxxxx
    Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
    Reviewed-by: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
    Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index ad6dc4f54ae7b..a0e34581a1cd6 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 ? Fail the request.
@@ -241,6 +241,11 @@ 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;
 }