From: Liang Wang wangliang101@huawei.com Subject: lib: use PFN_PHYS() in devmem_is_allowed()
The physical address may exceed 32 bits on 32-bit systems with more than 32 bits of physcial address. Use PFN_PHYS() in devmem_is_allowed(), or the physical address may overflow and be truncated.
We found this bug when mapping a high addresses through devmem tool, when CONFIG_STRICT_DEVMEM is enabled on the ARM with ARM_LPAE and devmem is used to map a high address that is not in the iomem address range, an unexpected error indicating no permission is returned.
This bug was initially introduced from v2.6.37, and the function was moved to lib when v5.11.
Link: https://lkml.kernel.org/r/20210731025057.78825-1-wangliang101@huawei.com Fixes: 087aaffcdf9c ("ARM: implement CONFIG_STRICT_DEVMEM by disabling access to RAM via /dev/mem") Fixes: 527701eda5f1 ("lib: Add a generic version of devmem_is_allowed()") Signed-off-by: Liang Wang wangliang101@huawei.com Reviewed-by: Luis Chamberlain mcgrof@kernel.org Cc: Palmer Dabbelt palmerdabbelt@google.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Russell King linux@armlinux.org.uk Cc: Liang Wang wangliang101@huawei.com Cc: Xiaoming Ni nixiaoming@huawei.com Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: stable@vger.kernel.org [2.6.37+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
lib/devmem_is_allowed.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/lib/devmem_is_allowed.c~lib-use-pfn_phys-in-devmem_is_allowed +++ a/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; _