From 119cd59fcfbe70fb3fcab4e64cd232bcc3807585 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 15 Feb 2020 19:54:56 -0500 Subject: [PATCH] x86: get rid of put_user_try in __setup_rt_frame() (both 32bit and 64bit) Straightforward, except for save_altstack_ex() stuck in those. Replace that thing with an analogue that would use unsafe_put_user() instead of put_user_ex() (called compat_save_altstack()) and be done with that. Signed-off-by: Al Viro --- arch/x86/kernel/signal.c | 91 +++++++++++++++++++++++++----------------------- include/linux/signal.h | 8 ++--- 2 files changed, 52 insertions(+), 47 deletions(-) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 29abad29aaa1..8b879fdc214c 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -365,38 +365,37 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig, frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate); - if (!access_ok(frame, sizeof(*frame))) + if (!user_access_begin(frame, sizeof(*frame))) return -EFAULT; - put_user_try { - put_user_ex(sig, &frame->sig); - put_user_ex(&frame->info, &frame->pinfo); - put_user_ex(&frame->uc, &frame->puc); + unsafe_put_user(sig, &frame->sig, Efault); + unsafe_put_user(&frame->info, &frame->pinfo, Efault); + unsafe_put_user(&frame->uc, &frame->puc, Efault); - /* Create the ucontext. */ - if (static_cpu_has(X86_FEATURE_XSAVE)) - put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags); - else - put_user_ex(0, &frame->uc.uc_flags); - put_user_ex(0, &frame->uc.uc_link); - save_altstack_ex(&frame->uc.uc_stack, regs->sp); + /* Create the ucontext. */ + if (static_cpu_has(X86_FEATURE_XSAVE)) + unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault); + else + unsafe_put_user(0, &frame->uc.uc_flags, Efault); + unsafe_put_user(0, &frame->uc.uc_link, Efault); + unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); - /* Set up to return from userspace. */ - restorer = current->mm->context.vdso + - vdso_image_32.sym___kernel_rt_sigreturn; - if (ksig->ka.sa.sa_flags & SA_RESTORER) - restorer = ksig->ka.sa.sa_restorer; - put_user_ex(restorer, &frame->pretcode); + /* Set up to return from userspace. */ + restorer = current->mm->context.vdso + + vdso_image_32.sym___kernel_rt_sigreturn; + if (ksig->ka.sa.sa_flags & SA_RESTORER) + restorer = ksig->ka.sa.sa_restorer; + unsafe_put_user(restorer, &frame->pretcode, Efault); - /* - * This is movl $__NR_rt_sigreturn, %ax ; int $0x80 - * - * WE DO NOT USE IT ANY MORE! It's only left here for historical - * reasons and because gdb uses it as a signature to notice - * signal handler stack frames. - */ - put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode); - } put_user_catch(err); + /* + * This is movl $__NR_rt_sigreturn, %ax ; int $0x80 + * + * WE DO NOT USE IT ANY MORE! It's only left here for historical + * reasons and because gdb uses it as a signature to notice + * signal handler stack frames. + */ + unsafe_put_user(*((u64 *)&rt_retcode), (u64 *)frame->retcode, Efault); + user_access_end(); err |= copy_siginfo_to_user(&frame->info, &ksig->info); err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate, @@ -419,6 +418,9 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig, regs->cs = __USER_CS; return 0; +Efault: + user_access_end(); + return -EFAULT; } #else /* !CONFIG_X86_32 */ static unsigned long frame_uc_flags(struct pt_regs *regs) @@ -444,6 +446,10 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig, unsigned long uc_flags; int err = 0; + /* x86-64 should always use SA_RESTORER. */ + if (!(ksig->ka.sa.sa_flags & SA_RESTORER)) + return -EFAULT; + frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp); if (!access_ok(frame, sizeof(*frame))) @@ -455,23 +461,18 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig, } uc_flags = frame_uc_flags(regs); + if (!user_access_begin(frame, sizeof(*frame))) + return -EFAULT; - put_user_try { - /* Create the ucontext. */ - put_user_ex(uc_flags, &frame->uc.uc_flags); - put_user_ex(0, &frame->uc.uc_link); - save_altstack_ex(&frame->uc.uc_stack, regs->sp); - - /* Set up to return from userspace. If provided, use a stub - already in userspace. */ - /* x86-64 should always use SA_RESTORER. */ - if (ksig->ka.sa.sa_flags & SA_RESTORER) { - put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode); - } else { - /* could use a vstub here */ - err |= -EFAULT; - } - } put_user_catch(err); + /* Create the ucontext. */ + unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault); + unsafe_put_user(0, &frame->uc.uc_link, Efault); + unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); + + /* Set up to return from userspace. If provided, use a stub + already in userspace. */ + unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault); + user_access_end(); err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]); err |= __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]); @@ -515,6 +516,10 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig, force_valid_ss(regs); return 0; + +Efault: + user_access_end(); + return -EFAULT; } #endif /* CONFIG_X86_32 */ diff --git a/include/linux/signal.h b/include/linux/signal.h index 1a5f88316b08..05bacd2ab135 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -444,12 +444,12 @@ void signals_init(void); int restore_altstack(const stack_t __user *); int __save_altstack(stack_t __user *, unsigned long); -#define save_altstack_ex(uss, sp) do { \ +#define unsafe_save_altstack(uss, sp, label) do { \ stack_t __user *__uss = uss; \ struct task_struct *t = current; \ - put_user_ex((void __user *)t->sas_ss_sp, &__uss->ss_sp); \ - put_user_ex(t->sas_ss_flags, &__uss->ss_flags); \ - put_user_ex(t->sas_ss_size, &__uss->ss_size); \ + unsafe_put_user((void __user *)t->sas_ss_sp, &__uss->ss_sp, label); \ + unsafe_put_user(t->sas_ss_flags, &__uss->ss_flags, label); \ + unsafe_put_user(t->sas_ss_size, &__uss->ss_size, label); \ if (t->sas_ss_flags & SS_AUTODISARM) \ sas_ss_reset(t); \ } while (0); -- 2.11.0