Patch "s390/mm: fix off-by-one bug in 5-level page table handling" has been added to the 4.14-stable tree

Patch "s390/mm: fix off-by-one bug in 5-level page table handling" has been added to the 4.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    s390/mm: fix off-by-one bug in 5-level page table handling

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-mm-fix-off-by-one-bug-in-5-level-page-table-handling.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 8d306f53b63099fec2d56300149e400d181ba4f5 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 4 Dec 2017 09:42:45 +0100
Subject: s390/mm: fix off-by-one bug in 5-level page table handling

From: Heiko Carstens <heiko.carstens@de.ibm.com>

commit 8d306f53b63099fec2d56300149e400d181ba4f5 upstream.

Martin Cermak reported that setting a uprobe doesn't work. Reason for
this is that the common uprobes code tries to get an unmapped area at
the last possible page within an address space.

This broke with commit 1aea9b3f9210 ("s390/mm: implement 5 level pages
tables") which introduced an off-by-one bug which prevents to map
anything at the last possible page within an address space.

The check with the off-by-one bug however can be removed since with
commit 8ab867cb0806 ("s390/mm: fix BUG_ON in crst_table_upgrade") the
necessary check is done at both call sites.

Reported-by: Martin Cermak <mcermak@redhat.com>
Bisected-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Fixes: 1aea9b3f9210 ("s390/mm: implement 5 level pages tables")
Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/s390/mm/pgalloc.c |    2 --
 1 file changed, 2 deletions(-)

--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -85,8 +85,6 @@ int crst_table_upgrade(struct mm_struct
 
 	/* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
 	VM_BUG_ON(mm->context.asce_limit < _REGION2_SIZE);
-	if (end >= TASK_SIZE_MAX)
-		return -ENOMEM;
 	rc = 0;
 	notify = 0;
 	while (mm->context.asce_limit < end) {


Patches currently in stable-queue which might be from heiko.carstens@de.ibm.com are

queue-4.14/s390-always-save-and-restore-all-registers-on-context-switch.patch
queue-4.14/s390-fix-compat-system-call-table.patch
queue-4.14/s390-mm-fix-off-by-one-bug-in-5-level-page-table-handling.patch