4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ard Biesheuvel ard.biesheuvel@linaro.org
commit 1598ecda7b239e9232dda032bfddeed9d89fab6c upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/kernel/kaslr.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- 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 @@ static __init u64 get_kaslr_seed(void *f 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 @@ u64 __init kaslr_early_init(u64 dt_phys) * 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 @@ u64 __init kaslr_early_init(u64 dt_phys) 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; }