The patch below does not apply to the 5.15-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-5.15.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 '2025101606-wildfire-moody-50d8@gregkh' --subject-prefix 'PATCH 5.15.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);