This is a note to let you know that I've just added the patch titled s390/mm: fix BUG_ON in crst_table_upgrade to the 4.12-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-bug_on-in-crst_table_upgrade.patch and it can be found in the queue-4.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 8ab867cb0806a8e195de161fd8883a0578d1d050 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Date: Thu, 31 Aug 2017 13:18:22 +0200 Subject: s390/mm: fix BUG_ON in crst_table_upgrade From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> commit 8ab867cb0806a8e195de161fd8883a0578d1d050 upstream. A 31-bit compat process can force a BUG_ON in crst_table_upgrade with specific, invalid mmap calls, e.g. mmap((void*) 0x7fff8000, 0x10000, 3, 32, -1, 0) The arch_get_unmapped_area[_topdown] functions miss an if condition in the decision to do a page table upgrade. [ms: Backport to 4.12, minor context change] Fixes: 9b11c7912d00 ("s390/mm: simplify arch_get_unmapped_area[_topdown]") Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/s390/mm/mmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/arch/s390/mm/mmap.c +++ b/arch/s390/mm/mmap.c @@ -119,7 +119,8 @@ arch_get_unmapped_area(struct file *filp return addr; check_asce_limit: - if (addr + len > current->mm->context.asce_limit) { + if (addr + len > current->mm->context.asce_limit && + addr + len <= TASK_SIZE) { rc = crst_table_upgrade(mm); if (rc) return (unsigned long) rc; @@ -183,7 +184,8 @@ arch_get_unmapped_area_topdown(struct fi } check_asce_limit: - if (addr + len > current->mm->context.asce_limit) { + if (addr + len > current->mm->context.asce_limit && + addr + len <= TASK_SIZE) { rc = crst_table_upgrade(mm); if (rc) return (unsigned long) rc; Patches currently in stable-queue which might be from schwidefsky@xxxxxxxxxx are queue-4.12/s390-mm-avoid-empty-zero-pages-for-kvm-guests-to-avoid-postcopy-hangs.patch queue-4.12/s390-mm-fix-bug_on-in-crst_table_upgrade.patch