FAILED: patch "[PATCH] s390/pci: Fix s390_pci_mmio_write syscall error return" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x b7ab86bdc65eadcfc43a0e3faf682a3f750cfb96
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026080501-police-riverboat-1b49@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From b7ab86bdc65eadcfc43a0e3faf682a3f750cfb96 Mon Sep 17 00:00:00 2001
From: Niklas Schnelle <[email protected]>
Date: Wed, 22 Jul 2026 15:08:34 +0200
Subject: [PATCH] s390/pci: Fix s390_pci_mmio_write syscall error return
 without MIO

On a machine without PCI memory-I/O (MIO) support or when running with
pci=nomio the s390 specific PCI MMIO write syscall checks if the MMIO
cookie is above ZPCI_IOMAP_ADDR_BASE as a sanity check before even
trying to perform the MMIO. If this check fails the return value was
left unchanged and thus 0 from prior operations falsely indicating
success. This could potentially confuse user-space into falsely
believing the MMIO, on a mapping not valid for MMIO was successful.

Fix this by setting the return value to -EFAULT prior to the check
following the same pattern as elsewhere in the same function.

Cc: [email protected]
Reviewed-by: Julian Ruess <[email protected]>
Reviewed-by: Farhan Ali <[email protected]>
Fixes: a67a88b0b8de ("s390/pci: remove races against pte updates")
Signed-off-by: Niklas Schnelle <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c
index 51e7a28af899..f3f79ba78410 100644
--- a/arch/s390/pci/pci_mmio.c
+++ b/arch/s390/pci/pci_mmio.c
@@ -188,6 +188,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr,
 			goto out_unlock_mmap;
 	}
 
+	ret = -EFAULT;
 	io_addr = (void __iomem *)((args.pfn << PAGE_SHIFT) |
 			(mmio_addr & ~PAGE_MASK));