FAILED: patch "[PATCH] xtensa: simdisk: add input size check in proc_write_simdisk" failed to apply to 5.10-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.10-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 <stable@vger.kernel.org>.

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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 5d5f08fd0cd970184376bee07d59f635c8403f63
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025101607-sift-throttle-b1aa@gregkh' --subject-prefix 'PATCH 5.10.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 <linmq006@gmail.com>
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()")

Fixes: b6c7e873daf7 ("xtensa: ISS: add host file-based simulated disk")
Fixes: 16e5c1fc3604 ("convert a bunch of open-coded instances of memdup_user_nul()")
Cc: stable@vger.kernel.org
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Message-Id: <20250829083015.1992751-1-linmq006@gmail.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --git a/arch/xtensa/platforms/iss/simdisk.c b/arch/xtensa/platforms/iss/simdisk.c
index 6ed009318d24..3cafc8feddee 100644
--- a/arch/xtensa/platforms/iss/simdisk.c
+++ b/arch/xtensa/platforms/iss/simdisk.c
@@ -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);