linux-kernel - [PATCH] s390/mm: return -ENOMEM in arch_get_unmapped_area[

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Message-Id: <20171026073610.9139-1-liwang@redhat.com>
Date:   Thu, 26 Oct 2017 15:36:10 +0800
From:   Li Wang <liwang@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Cc:     schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        mingo@...nel.org, hughd@...gle.com, paul.gortmaker@...driver.com,
        mhocko@...e.com, shuwang@...hat.com, liwang@...hat.com
Subject: [PATCH] s390/mm: return -ENOMEM in arch_get_unmapped_area[_topdown]

That would be very hard to get -ENOMEM returned in crst_table_upgrade()
because the condition(addr + len <= TASK_SIZE) makes all 'end' value
is smaller/equal than 'TASK_SIZE_TASK'. So let's move it to the upper
layer.

Fixes: 8ab867cb0806 (s390/mm: fix BUG_ON in crst_table_upgrade)
Signed-off-by: Li Wang <liwang@...hat.com>
---
 arch/s390/mm/mmap.c    | 6 ++++++
 arch/s390/mm/pgalloc.c | 3 +--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 5bea139..8ddb13a 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -119,6 +119,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 		return addr;
 
 check_asce_limit:
+	if (addr + len >= TASK_SIZE_MAX)
+		return -ENOMEM;
+
 	if (addr + len > current->mm->context.asce_limit &&
 	    addr + len <= TASK_SIZE) {
 		rc = crst_table_upgrade(mm, addr + len);
@@ -184,6 +187,9 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	}
 
 check_asce_limit:
+	if (addr + len >= TASK_SIZE_MAX)
+		return -ENOMEM;
+
 	if (addr + len > current->mm->context.asce_limit &&
 	    addr + len <= TASK_SIZE) {
 		rc = crst_table_upgrade(mm, addr + len);
diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
index 05f1f27..5e4b887 100644
--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -84,8 +84,7 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
 
 	/* 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) {
-- 
2.9.3