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.

Cc: Luis Chamberlain mcgrof@kernel.org 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()") Cc: stable@vger.kernel.org # v2.6.37 Signed-off-by: Liang Wang wangliang101@huawei.com --- v3: update changelog suggested by Luis Chamberlain mcgrof@kernel.org 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;