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

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 <[email protected]> know about it.

From: Heiko Carstens <[email protected]>
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 <[email protected]>

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.

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

@@ -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 [email protected] 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