From b7ab86bdc65eadcfc43a0e3faf682a3f750cfb96 Mon Sep 17 00:00:00 2001 From: Niklas Schnelle 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: stable@vger.kernel.org Reviewed-by: Julian Ruess Reviewed-by: Farhan Ali Fixes: a67a88b0b8de ("s390/pci: remove races against pte updates") Signed-off-by: Niklas Schnelle Signed-off-by: Vasily Gorbik --- arch/s390/pci/pci_mmio.c | 1 + 1 file changed, 1 insertion(+) 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));