The patch below does not apply to the 4.9-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.

thanks,

greg k-h

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

From 41ac42f137080bc230b5882e3c88c392ab7f2d32 Mon Sep 17 00:00:00 2001 From: Gerald Schaefer gerald.schaefer@linux.ibm.com Date: Wed, 17 Aug 2022 15:26:03 +0200 Subject: [PATCH] s390/mm: do not trigger write fault when vma does not allow VM_WRITE

For non-protection pXd_none() page faults in do_dat_exception(), we call do_exception() with access == (VM_READ | VM_WRITE | VM_EXEC). In do_exception(), vma->vm_flags is checked against that before calling handle_mm_fault().

Since commit 92f842eac7ee3 ("[S390] store indication fault optimization"), we call handle_mm_fault() with FAULT_FLAG_WRITE, when recognizing that it was a write access. However, the vma flags check is still only checking against (VM_READ | VM_WRITE | VM_EXEC), and therefore also calling handle_mm_fault() with FAULT_FLAG_WRITE in cases where the vma does not allow VM_WRITE.

Fix this by changing access check in do_exception() to VM_WRITE only, when recognizing write access.

Link: https://lkml.kernel.org/r/20220811103435.188481-3-david@redhat.com Fixes: 92f842eac7ee3 ("[S390] store indication fault optimization") Cc: stable@vger.kernel.org Reported-by: David Hildenbrand david@redhat.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Gerald Schaefer gerald.schaefer@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index 13449941516c..09b6e756d521 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -379,7 +379,9 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access) flags = FAULT_FLAG_DEFAULT; if (user_mode(regs)) flags |= FAULT_FLAG_USER; - if (access == VM_WRITE || is_write) + if (is_write) + access = VM_WRITE; + if (access == VM_WRITE) flags |= FAULT_FLAG_WRITE; mmap_read_lock(mm);