arm64: kaslr: ensure randomized quantities are clean to the PoC
kaslr_early_init() is called with the kernel mapped at its
link time offset, and if it returns with a non-zero offset,
the kernel is unmapped and remapped again at the randomized
offset.
During its execution, kaslr_early_init() also randomizes the
base of the module region and of the linear mapping of DRAM,
and sets two variables accordingly. However, since these
variables are assigned with the caches on, they may get lost
during the cache maintenance that occurs when unmapping and
remapping the kernel, so ensure that these values are cleaned
to the PoC.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: f80fb3a3d508 ("arm64: add support for kernel ASLR")
Cc: <stable@vger.kernel.org> # v4.6+
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index f0e6ab8..ba6b417 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -14,6 +14,7 @@
#include <linux/sched.h>
#include <linux/types.h>
+#include <asm/cacheflush.h>
#include <asm/fixmap.h>
#include <asm/kernel-pgtable.h>
#include <asm/memory.h>
@@ -43,7 +44,7 @@
return ret;
}
-static __init const u8 *get_cmdline(void *fdt)
+static __init const u8 *kaslr_get_cmdline(void *fdt)
{
static __initconst const u8 default_cmdline[] = CONFIG_CMDLINE;
@@ -109,7 +110,7 @@
* Check if 'nokaslr' appears on the command line, and
* return 0 if that is the case.
*/
- cmdline = get_cmdline(fdt);
+ cmdline = kaslr_get_cmdline(fdt);
str = strstr(cmdline, "nokaslr");
if (str == cmdline || (str > cmdline && *(str - 1) == ' '))
return 0;
@@ -169,5 +170,8 @@
module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;
module_alloc_base &= PAGE_MASK;
+ __flush_dcache_area(&module_alloc_base, sizeof(module_alloc_base));
+ __flush_dcache_area(&memstart_offset_seed, sizeof(memstart_offset_seed));
+
return offset;
}