From 8ab867cb0806a8e195de161fd8883a0578d1d050 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Thu, 31 Aug 2017 13:18:22 +0200 Subject: [PATCH] s390/mm: fix BUG_ON in crst_table_upgrade 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. Fixes: 9b11c7912d00 ("s390/mm: simplify arch_get_unmapped_area[_topdown]") Cc: # v4.12+ Signed-off-by: Martin Schwidefsky --- arch/s390/mm/mmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c index 2e10d2b8ad35..5bea139517a2 100644 --- a/arch/s390/mm/mmap.c +++ b/arch/s390/mm/mmap.c @@ -119,7 +119,8 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, 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, addr + len); if (rc) return (unsigned long) rc; @@ -183,7 +184,8 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, } 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, addr + len); if (rc) return (unsigned long) rc; -- 2.30.2