Patch "cachefiles: add consistency check for copen/cread" 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: add consistency check for copen/cread

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-add-consistency-check-for-copen-cread.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 8bc633bbb37a775245eeea1fddef64625d839e38
Author: Baokun Li <libaokun1@xxxxxxxxxx>
Date:   Wed May 22 19:43:02 2024 +0800

    cachefiles: add consistency check for copen/cread
    
    [ Upstream commit a26dc49df37e996876f50a0210039b2d211fdd6f ]
    
    This prevents malicious processes from completing random copen/cread
    requests and crashing the system. Added checks are listed below:
    
      * Generic, copen can only complete open requests, and cread can only
        complete read requests.
      * For copen, ondemand_id must not be 0, because this indicates that the
        request has not been read by the daemon.
      * For cread, the object corresponding to fd and req should be the same.
    
    Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240522114308.2402121-7-libaokun@xxxxxxxxxxxxxxx
    Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
    Reviewed-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
    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 7e4874f60de10..ad6dc4f54ae7b 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -97,12 +97,12 @@ 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;
@@ -110,10 +110,15 @@ 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);
@@ -142,6 +147,7 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 	unsigned long id;
 	long size;
 	int ret;
+	XA_STATE(xas, &cache->reqs, 0);
 
 	if (!test_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags))
 		return -EOPNOTSUPP;
@@ -165,9 +171,16 @@ 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);
 
 	/* fail OPEN request if copen format is invalid */
 	ret = kstrtol(psize, 0, &size);