linux-kernel - [PATCH v2 2/4] um: Fix potential integer overflow during physmem setup

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Message-Id: <20240916045950.508910-3-tiwei.btw@antgroup.com>
Date: Mon, 16 Sep 2024 12:59:48 +0800
From: "Tiwei Bie" <tiwei.btw@...group.com>
To: richard@....at,
	anton.ivanov@...bridgegreys.com,
	johannes@...solutions.net
Cc:  <linux-um@...ts.infradead.org>,
   <linux-kernel@...r.kernel.org>,
   <benjamin@...solutions.net>,
  "Tiwei Bie" <tiwei.btw@...group.com>
Subject: [PATCH v2 2/4] um: Fix potential integer overflow during physmem setup

This issue happens when the real map size is greater than LONG_MAX,
which can be easily triggered on UML/i386.

Fixes: fe205bdd1321 ("um: Print minimum physical memory requirement")
Signed-off-by: Tiwei Bie <tiwei.btw@...group.com>
---
 arch/um/kernel/physmem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
index fb2adfb49945..ee693e0b2b58 100644
--- a/arch/um/kernel/physmem.c
+++ b/arch/um/kernel/physmem.c
@@ -81,10 +81,10 @@ void __init setup_physmem(unsigned long start, unsigned long reserve_end,
 			  unsigned long len, unsigned long long highmem)
 {
 	unsigned long reserve = reserve_end - start;
-	long map_size = len - reserve;
+	unsigned long map_size = len - reserve;
 	int err;
 
-	if(map_size <= 0) {
+	if (len <= reserve) {
 		os_warn("Too few physical memory! Needed=%lu, given=%lu\n",
 			reserve, len);
 		exit(1);
@@ -95,7 +95,7 @@ void __init setup_physmem(unsigned long start, unsigned long reserve_end,
 	err = os_map_memory((void *) reserve_end, physmem_fd, reserve,
 			    map_size, 1, 1, 1);
 	if (err < 0) {
-		os_warn("setup_physmem - mapping %ld bytes of memory at 0x%p "
+		os_warn("setup_physmem - mapping %lu bytes of memory at 0x%p "
 			"failed - errno = %d\n", map_size,
 			(void *) reserve_end, err);
 		exit(1);
-- 
2.34.1