diff options
| -rw-r--r-- | arch/arm64/Kconfig | 7 | ||||
| -rw-r--r-- | arch/arm64/kernel/kaslr.c | 20 | ||||
| -rw-r--r-- | arch/arm64/kernel/module.c | 7 | ||||
| -rw-r--r-- | include/linux/sizes.h | 4 |
4 files changed, 23 insertions, 15 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 655c0e99d9fa..b4234ddf6570 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1110,7 +1110,6 @@ config ARM64_MODULE_CMODEL_LARGE config ARM64_MODULE_PLTS bool - select ARM64_MODULE_CMODEL_LARGE select HAVE_MOD_ARCH_SPECIFIC config RELOCATABLE @@ -1144,12 +1143,12 @@ config RANDOMIZE_BASE If unsure, say N. config RANDOMIZE_MODULE_REGION_FULL - bool "Randomize the module region independently from the core kernel" + bool "Randomize the module region over a 4 GB range" depends on RANDOMIZE_BASE default y help - Randomizes the location of the module region without considering the - location of the core kernel. This way, it is impossible for modules + Randomizes the location of the module region inside a 4 GB window + covering the core kernel. This way, it is less likely for modules to leak information about the location of core kernel data structures but it does imply that function calls between modules and the core kernel will need to be resolved via veneers in the module PLT. diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index e3d5cbe2167b..f0e6ab8abe9c 100644 --- a/arch/arm64/kernel/kaslr.c +++ b/arch/arm64/kernel/kaslr.c @@ -117,13 +117,15 @@ u64 __init kaslr_early_init(u64 dt_phys) /* * OK, so we are proceeding with KASLR enabled. Calculate a suitable * kernel image offset from the seed. Let's place the kernel in the - * lower half of the VMALLOC area (VA_BITS - 2). + * middle half of the VMALLOC area (VA_BITS - 2), and stay clear of + * the lower and upper quarters to avoid colliding with other + * allocations. * Even if we could randomize at page granularity for 16k and 64k pages, * let's always round to 2 MB so we don't interfere with the ability to * map using contiguous PTEs */ mask = ((1UL << (VA_BITS - 2)) - 1) & ~(SZ_2M - 1); - offset = seed & mask; + offset = BIT(VA_BITS - 3) + (seed & mask); /* use the top 16 bits to randomize the linear region */ memstart_offset_seed = seed >> 48; @@ -134,21 +136,23 @@ u64 __init kaslr_early_init(u64 dt_phys) * vmalloc region, since shadow memory is allocated for each * module at load time, whereas the vmalloc region is shadowed * by KASAN zero pages. So keep modules out of the vmalloc - * region if KASAN is enabled. + * region if KASAN is enabled, and put the kernel well within + * 4 GB of the module region. */ - return offset; + return offset % SZ_2G; if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) { /* - * Randomize the module region independently from the core - * kernel. This prevents modules from leaking any information + * Randomize the module region over a 4 GB window covering the + * kernel. This reduces the risk of modules leaking information * about the address of the kernel itself, but results in * branches between modules and the core kernel that are * resolved via PLTs. (Branches between modules will be * resolved normally.) */ - module_range = VMALLOC_END - VMALLOC_START - MODULES_VSIZE; - module_alloc_base = VMALLOC_START; + module_range = SZ_4G - (u64)(_end - _stext); + module_alloc_base = max((u64)_end + offset - SZ_4G, + (u64)MODULES_VADDR); } else { /* * Randomize the module region by setting module_alloc_base to diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c index c8c6c2828b79..70c3e5518e95 100644 --- a/arch/arm64/kernel/module.c +++ b/arch/arm64/kernel/module.c @@ -55,9 +55,10 @@ void *module_alloc(unsigned long size) * less likely that the module region gets exhausted, so we * can simply omit this fallback in that case. */ - p = __vmalloc_node_range(size, MODULE_ALIGN, VMALLOC_START, - VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_EXEC, 0, - NUMA_NO_NODE, __builtin_return_address(0)); + p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base, + module_alloc_base + SZ_4G, GFP_KERNEL, + PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, + __builtin_return_address(0)); if (p && (kasan_module_alloc(p, size) < 0)) { vfree(p); diff --git a/include/linux/sizes.h b/include/linux/sizes.h index ce3e8150c174..fbde0bc7e882 100644 --- a/include/linux/sizes.h +++ b/include/linux/sizes.h @@ -8,6 +8,8 @@ #ifndef __LINUX_SIZES_H__ #define __LINUX_SIZES_H__ +#include <linux/const.h> + #define SZ_1 0x00000001 #define SZ_2 0x00000002 #define SZ_4 0x00000004 @@ -44,4 +46,6 @@ #define SZ_1G 0x40000000 #define SZ_2G 0x80000000 +#define SZ_4G _AC(0x100000000, ULL) + #endif /* __LINUX_SIZES_H__ */ |