FAILED: patch "[PATCH] xtensa: simdisk: add input size check in proc_write_simdisk" 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 5d5f08fd0cd970184376bee07d59f635c8403f63
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025101607-uncivil-cartload-f9ef@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 5d5f08fd0cd970184376bee07d59f635c8403f63 Mon Sep 17 00:00:00 2001
From: Miaoqian Lin <[email protected]>
Date: Fri, 29 Aug 2025 16:30:15 +0800
Subject: [PATCH] xtensa: simdisk: add input size check in proc_write_simdisk

A malicious user could pass an arbitrarily bad value to memdup_user_nul(), potentially causing kernel crash.

This follows the same pattern as commit ee76746387f6 ("netdevsim: prevent bad user input in nsim_dev_health_break_write()")

Message-Id: <[email protected]>

index 6ed009318d24..3cafc8feddee 100644
@@ -231,10 +231,14 @@ static ssize_t proc_read_simdisk(struct file *file, char __user *buf,
 static ssize_t proc_write_simdisk(struct file *file, const char __user *buf,
 			size_t count, loff_t *ppos)
 {
-	char *tmp = memdup_user_nul(buf, count);
+	char *tmp;
 	struct simdisk *dev = pde_data(file_inode(file));
 	int err;
 
+	if (count == 0 || count > PAGE_SIZE)
+		return -EINVAL;
+
+	tmp = memdup_user_nul(buf, count);
 	if (IS_ERR(tmp))
 		return PTR_ERR(tmp);