From a1d5ebaf8ccdd100f45042ce32c591867de04ac3 Mon Sep 17 00:00:00 2001 From: Matthew Leach Date: Fri, 11 Oct 2013 14:52:14 +0100 Subject: [PATCH] arm64: big-endian: don't treat code as data when copying sigret code Currently the sigreturn compat code is copied to an offset in the vectors table. When using a BE kernel this data will be stored in the wrong endianess so when returning from a signal on a 32-bit BE system, arbitrary code will be executed. Instead of declaring the code inside a struct and copying that, use the assembler's .byte directives to store the code in the correct endianess regardless of platform endianess. Acked-by: Will Deacon Signed-off-by: Matthew Leach Signed-off-by: Catalin Marinas --- arch/arm64/kernel/kuser32.S | 42 ++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/signal32.c | 28 ------------------------ arch/arm64/kernel/vdso.c | 5 ++++- 3 files changed, 46 insertions(+), 29 deletions(-) diff --git a/arch/arm64/kernel/kuser32.S b/arch/arm64/kernel/kuser32.S index 8b69ecb1d8bc..1e4905d52d30 100644 --- a/arch/arm64/kernel/kuser32.S +++ b/arch/arm64/kernel/kuser32.S @@ -27,6 +27,9 @@ * * See Documentation/arm/kernel_user_helpers.txt for formal definitions. */ + +#include + .align 5 .globl __kuser_helper_start __kuser_helper_start: @@ -75,3 +78,42 @@ __kuser_helper_version: // 0xffff0ffc .word ((__kuser_helper_end - __kuser_helper_start) >> 5) .globl __kuser_helper_end __kuser_helper_end: + +/* + * AArch32 sigreturn code + * + * For ARM syscalls, the syscall number has to be loaded into r7. + * We do not support an OABI userspace. + * + * For Thumb syscalls, we also pass the syscall number via r7. We therefore + * need two 16-bit instructions. + */ + .globl __aarch32_sigret_code_start +__aarch32_sigret_code_start: + + /* + * ARM Code + */ + .byte __NR_compat_sigreturn, 0x70, 0xa0, 0xe3 // mov r7, #__NR_compat_sigreturn + .byte __NR_compat_sigreturn, 0x00, 0x00, 0xef // svc #__NR_compat_sigreturn + + /* + * Thumb code + */ + .byte __NR_compat_sigreturn, 0x27 // svc #__NR_compat_sigreturn + .byte __NR_compat_sigreturn, 0xdf // mov r7, #__NR_compat_sigreturn + + /* + * ARM code + */ + .byte __NR_compat_rt_sigreturn, 0x70, 0xa0, 0xe3 // mov r7, #__NR_compat_rt_sigreturn + .byte __NR_compat_rt_sigreturn, 0x00, 0x00, 0xef // svc #__NR_compat_rt_sigreturn + + /* + * Thumb code + */ + .byte __NR_compat_rt_sigreturn, 0x27 // svc #__NR_compat_rt_sigreturn + .byte __NR_compat_rt_sigreturn, 0xdf // mov r7, #__NR_compat_rt_sigreturn + + .globl __aarch32_sigret_code_end +__aarch32_sigret_code_end: diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c index e393174fe859..e8772c07cf5c 100644 --- a/arch/arm64/kernel/signal32.c +++ b/arch/arm64/kernel/signal32.c @@ -100,34 +100,6 @@ struct compat_rt_sigframe { #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP))) -/* - * For ARM syscalls, the syscall number has to be loaded into r7. - * We do not support an OABI userspace. - */ -#define MOV_R7_NR_SIGRETURN (0xe3a07000 | __NR_compat_sigreturn) -#define SVC_SYS_SIGRETURN (0xef000000 | __NR_compat_sigreturn) -#define MOV_R7_NR_RT_SIGRETURN (0xe3a07000 | __NR_compat_rt_sigreturn) -#define SVC_SYS_RT_SIGRETURN (0xef000000 | __NR_compat_rt_sigreturn) - -/* - * For Thumb syscalls, we also pass the syscall number via r7. We therefore - * need two 16-bit instructions. - */ -#define SVC_THUMB_SIGRETURN (((0xdf00 | __NR_compat_sigreturn) << 16) | \ - 0x2700 | __NR_compat_sigreturn) -#define SVC_THUMB_RT_SIGRETURN (((0xdf00 | __NR_compat_rt_sigreturn) << 16) | \ - 0x2700 | __NR_compat_rt_sigreturn) - -const compat_ulong_t aarch32_sigret_code[6] = { - /* - * AArch32 sigreturn code. - * We don't construct an OABI SWI - instead we just set the imm24 field - * to the EABI syscall number so that we create a sane disassembly. - */ - MOV_R7_NR_SIGRETURN, SVC_SYS_SIGRETURN, SVC_THUMB_SIGRETURN, - MOV_R7_NR_RT_SIGRETURN, SVC_SYS_RT_SIGRETURN, SVC_THUMB_RT_SIGRETURN, -}; - static inline int put_sigset_t(compat_sigset_t __user *uset, sigset_t *set) { compat_sigset_t cset; diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c index 6a389dc1bd49..65d40cf6945a 100644 --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -58,7 +58,10 @@ static struct page *vectors_page[1]; static int alloc_vectors_page(void) { extern char __kuser_helper_start[], __kuser_helper_end[]; + extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[]; + int kuser_sz = __kuser_helper_end - __kuser_helper_start; + int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start; unsigned long vpage; vpage = get_zeroed_page(GFP_ATOMIC); @@ -72,7 +75,7 @@ static int alloc_vectors_page(void) /* sigreturn code */ memcpy((void *)vpage + AARCH32_KERN_SIGRET_CODE_OFFSET, - aarch32_sigret_code, sizeof(aarch32_sigret_code)); + __aarch32_sigret_code_start, sigret_sz); flush_icache_range(vpage, vpage + PAGE_SIZE); vectors_page[0] = virt_to_page(vpage); -- 2.39.5