FAILED: patch "[PATCH] s390/pkey: Prevent overflow in size calculation for" 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 7360ee47599af91a1d5f4e74d635d9408a54e489
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025062906-tightwad-overvalue-2006@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 7360ee47599af91a1d5f4e74d635d9408a54e489 Mon Sep 17 00:00:00 2001
From: Fedor Pchelkin <[email protected]>
Date: Wed, 11 Jun 2025 22:20:10 +0300
Subject: [PATCH] s390/pkey: Prevent overflow in size calculation for
memdup_user()

Number of apqn target list entries contained in 'nr_apqns' variable is determined by userspace via an ioctl call so the result of the product in calculation of size passed to memdup_user() may overflow.

In this case the actual size of the allocated area and the value describing it won't be in sync leading to various types of unpredictable behaviour later.

Use a proper memdup_array_user() helper which returns an error if an overflow is detected. Note that it is different from when nr_apqns is initially zero - that case is considered valid and should be handled in subsequent pkey_handler implementations.

Found by Linux Verification Center (linuxtesting.org).

index cef60770f68b..b3fcdcae379e 100644
@@ -86,7 +86,7 @@ static void *_copy_apqns_from_user(void __user *uapqns, size_t nr_apqns)
 	if (!uapqns || nr_apqns == 0)
 		return NULL;
 
-	return memdup_user(uapqns, nr_apqns * sizeof(struct pkey_apqn));
+	return memdup_array_user(uapqns, nr_apqns, sizeof(struct pkey_apqn));
 }
 
 static int pkey_ioctl_genseck(struct pkey_genseck __user *ugs)

Hi Greg,

The main reason for the failure is, that the error-path implementation has changed after 5.4. But even if the patch is adopted accordingly, it will still require memdup_array_user(), which is currently missing in 5.4.y and 5.10.y (see my comment to the patch for 5.10.y).

Mit freundlichen Grüßen / Kind regards
Holger Dengler
--
IBM Systems, Linux on IBM Z Development
[email protected]