linux-kernel - [RFC PATCH 1/6] ARC: mm/mmap.c: Check length of unmapped area before allowing MAP

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Date:   Mon, 6 Dec 2021 15:02:52 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Liam Howlett <liam.howlett@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vineet Gupta <vgupta@...nel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: [RFC PATCH 1/6] ARC: 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: 5bba49f5397c (ARC: [mm] Aliasing VIPT dcache support 4/4)
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 arch/arc/mm/mmap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arc/mm/mmap.c b/arch/arc/mm/mmap.c
index 722d26b94307..1d7076406c4e 100644
--- a/arch/arc/mm/mmap.c
+++ b/arch/arc/mm/mmap.c
@@ -35,6 +35,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 	int aliasing = cache_is_vipt_aliasing();
 	struct vm_unmapped_area_info info;
 
+	if (len > TASK_SIZE)
+		return -ENOMEM;
+
 	/*
 	 * We only need to do colour alignment if D cache aliases.
 	 */
@@ -51,9 +54,6 @@ 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