Re: [PATCH] s390/pci: Fix s390_pci_mmio_write syscall error return without MIO

[sashiko-bot@kernel.org]

> 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 <julianr@linux.ibm.com>
> Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
> Fixes: a67a88b0b8de ("s390/pci: remove races against pte updates")
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260722-b4-syscall_mmio_ret_fix_upstream-v1-1-6de516b33001@linux.ibm.com?part=1