linux-kernel - [RFC PATCH 3/6] nds32/mm/mmap.c: Check length of unmapped area before allowing MAP

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Message-ID: <20211206150231.2283069-4-Liam.Howlett@oracle.com>
Date:   Mon, 6 Dec 2021 15:02:53 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Liam Howlett <liam.howlett@...cle.com>,
        Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 3/6] nds32/mm/mmap.c: Check length of unmapped area before
 allowing MAP_FIXED

arch_get_unmapped_area() could potentially allow a larger than possible
length when using the MAP_FIXED flag.  The bound check should come
before the check for MAP_FIXED.

Fixes: 664eec400bf8 (nds32: MMU fault handling and page table
management)
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 arch/nds32/mm/mmap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/nds32/mm/mmap.c b/arch/nds32/mm/mmap.c
index 1bdf5e7d1b43..1bc5a82ac3d3 100644
--- a/arch/nds32/mm/mmap.c
+++ b/arch/nds32/mm/mmap.c
@@ -31,6 +31,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 	if(IS_ENABLED(CONFIG_CPU_CACHE_ALIASING))
 		aliasing = 1;
 
+	if (len > TASK_SIZE)
+		return -ENOMEM;
+
 	/*
 	 * We only need to do colour alignment if either the I or D
 	 * caches alias.
@@ -48,9 +51,6 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 		return addr;
 	}
 
-	if (len > TASK_SIZE)
-		return -ENOMEM;
-
 	if (addr) {
 		if (do_align)
 			addr = COLOUR_ALIGN(addr, pgoff);
-- 
2.30.2