FAILED: patch "[PATCH] misc: fastrpc: Fix fastrpc_map_lookup operation" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 9031626ade38b092b72638dfe0c6ffce8d8acd43
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025101348-drapery-clean-43c1@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9031626ade38b092b72638dfe0c6ffce8d8acd43 Mon Sep 17 00:00:00 2001
From: Ling Xu <[email protected]>
Date: Fri, 12 Sep 2025 14:12:34 +0100
Subject: [PATCH] misc: fastrpc: Fix fastrpc_map_lookup operation

Fastrpc driver creates maps for user allocated fd buffers. Before creating a new map, the map list is checked for any already existing maps using map fd. Checking with just map fd is not sufficient as the user can pass offsetted buffer with less size when the map is created and then a larger size the next time which could result in memory issues. Check for dma_buf object also when looking up for the map.

index 52571916acd4..1815b1e0c607 100644
@@ -367,11 +367,16 @@ static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd,
 {
 	struct fastrpc_session_ctx *sess = fl->sctx;
 	struct fastrpc_map *map = NULL;
+	struct dma_buf *buf;
 	int ret = -ENOENT;
 
+	buf = dma_buf_get(fd);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
 	spin_lock(&fl->lock);
 	list_for_each_entry(map, &fl->maps, node) {
-		if (map->fd != fd)
+		if (map->fd != fd || map->buf != buf)
 			continue;
 
 		if (take_ref) {