linux-kernel - [PATCH] arm:mmap: fix physical address overflow when CONFIG_ARM

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Date:   Thu, 15 Jul 2021 20:20:03 +0800
From:   Liang Wang <wangliang101@...wei.com>
To:     <palmerdabbelt@...gle.com>, <mcgrof@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <wangle6@...wei.com>, <kepler.chenxin@...wei.com>,
        <nixiaoming@...wei.com>
Subject: [PATCH] arm:mmap: fix physical address overflow when CONFIG_ARM_LPAE=y

When the CONFIG_ARM_LPAE is enabled on arm32, the physical address may
exceed 32 bits. In the devmem_is_allowed function, the physical address
is obtained through displacement of the physical page number.Without
explicit translation, the physical address may overflow and be truncated.
Use the PFN_PHYS macro to fix this bug.

This bug was initially introduced in v2.6.37 with commit:087aaffcdf9c91.
In v5.10, this code has been modified by commit:527701eda5f196.

Fixes: 527701eda5f196 ("lib: Add a generic version of devmem_is_allowed")
Fixes: 087aaffcdf9c91 ("ARM: implement CONFIG_STRICT_DEVMEM by disabling access to RAM via /dev/mem")
Cc: stable@...r.kernel.org # v2.6.37
Signed-off-by: Liang Wang <wangliang101@...wei.com>
---
 lib/devmem_is_allowed.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/devmem_is_allowed.c b/lib/devmem_is_allowed.c
index c0d67c541849..60be9e24bd57 100644
--- a/lib/devmem_is_allowed.c
+++ b/lib/devmem_is_allowed.c
@@ -19,7 +19,7 @@
  */
 int devmem_is_allowed(unsigned long pfn)
 {
-	if (iomem_is_exclusive(pfn << PAGE_SHIFT))
+	if (iomem_is_exclusive(PFN_PHYS(pfn)))
 		return 0;
 	if (!page_is_ram(pfn))
 		return 1;
-- 
2.32.0