diff options
Diffstat (limited to 'arch/x86/kernel/signal.c')
| -rw-r--r-- | arch/x86/kernel/signal.c | 1006 |
1 files changed, 1006 insertions, 0 deletions
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c new file mode 100644 index 000000000..55ed638cb --- /dev/null +++ b/arch/x86/kernel/signal.c @@ -0,0 +1,1006 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs + * + * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson + * 2000-06-20 Pentium III FXSR, SSE support by Gareth Hughes + * 2000-2002 x86-64 support by Andi Kleen + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/sched.h> +#include <linux/sched/task_stack.h> +#include <linux/mm.h> +#include <linux/smp.h> +#include <linux/kernel.h> +#include <linux/kstrtox.h> +#include <linux/errno.h> +#include <linux/wait.h> +#include <linux/unistd.h> +#include <linux/stddef.h> +#include <linux/personality.h> +#include <linux/uaccess.h> +#include <linux/user-return-notifier.h> +#include <linux/uprobes.h> +#include <linux/context_tracking.h> +#include <linux/entry-common.h> +#include <linux/syscalls.h> + +#include <asm/processor.h> +#include <asm/ucontext.h> +#include <asm/fpu/signal.h> +#include <asm/fpu/xstate.h> +#include <asm/vdso.h> +#include <asm/mce.h> +#include <asm/sighandling.h> +#include <asm/vm86.h> + +#ifdef CONFIG_X86_64 +#include <linux/compat.h> +#include <asm/proto.h> +#include <asm/ia32_unistd.h> +#include <asm/fpu/xstate.h> +#endif /* CONFIG_X86_64 */ + +#include <asm/syscall.h> +#include <asm/sigframe.h> +#include <asm/signal.h> + +#ifdef CONFIG_X86_64 +/* + * If regs->ss will cause an IRET fault, change it. Otherwise leave it + * alone. Using this generally makes no sense unless + * user_64bit_mode(regs) would return true. + */ +static void force_valid_ss(struct pt_regs *regs) +{ + u32 ar; + asm volatile ("lar %[old_ss], %[ar]\n\t" + "jz 1f\n\t" /* If invalid: */ + "xorl %[ar], %[ar]\n\t" /* set ar = 0 */ + "1:" + : [ar] "=r" (ar) + : [old_ss] "rm" ((u16)regs->ss)); + + /* + * For a valid 64-bit user context, we need DPL 3, type + * read-write data or read-write exp-down data, and S and P + * set. We can't use VERW because VERW doesn't check the + * P bit. + */ + ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK; + if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) && + ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN)) + regs->ss = __USER_DS; +} +# define CONTEXT_COPY_SIZE offsetof(struct sigcontext, reserved1) +#else +# define CONTEXT_COPY_SIZE sizeof(struct sigcontext) +#endif + +static bool restore_sigcontext(struct pt_regs *regs, + struct sigcontext __user *usc, + unsigned long uc_flags) +{ + struct sigcontext sc; + + /* Always make any pending restarted system calls return -EINTR */ + current->restart_block.fn = do_no_restart_syscall; + + if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE)) + return false; + +#ifdef CONFIG_X86_32 + loadsegment(gs, sc.gs); + regs->fs = sc.fs; + regs->es = sc.es; + regs->ds = sc.ds; +#endif /* CONFIG_X86_32 */ + + regs->bx = sc.bx; + regs->cx = sc.cx; + regs->dx = sc.dx; + regs->si = sc.si; + regs->di = sc.di; + regs->bp = sc.bp; + regs->ax = sc.ax; + regs->sp = sc.sp; + regs->ip = sc.ip; + +#ifdef CONFIG_X86_64 + regs->r8 = sc.r8; + regs->r9 = sc.r9; + regs->r10 = sc.r10; + regs->r11 = sc.r11; + regs->r12 = sc.r12; + regs->r13 = sc.r13; + regs->r14 = sc.r14; + regs->r15 = sc.r15; +#endif /* CONFIG_X86_64 */ + + /* Get CS/SS and force CPL3 */ + regs->cs = sc.cs | 0x03; + regs->ss = sc.ss | 0x03; + + regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS); + /* disable syscall checks */ + regs->orig_ax = -1; + +#ifdef CONFIG_X86_64 + /* + * Fix up SS if needed for the benefit of old DOSEMU and + * CRIU. + */ + if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs))) + force_valid_ss(regs); +#endif + + return fpu__restore_sig((void __user *)sc.fpstate, + IS_ENABLED(CONFIG_X86_32)); +} + +static __always_inline int +__unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate, + struct pt_regs *regs, unsigned long mask) +{ +#ifdef CONFIG_X86_32 + unsigned int gs; + savesegment(gs, gs); + + unsafe_put_user(gs, (unsigned int __user *)&sc->gs, Efault); + unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault); + unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault); + unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault); +#endif /* CONFIG_X86_32 */ + + unsafe_put_user(regs->di, &sc->di, Efault); + unsafe_put_user(regs->si, &sc->si, Efault); + unsafe_put_user(regs->bp, &sc->bp, Efault); + unsafe_put_user(regs->sp, &sc->sp, Efault); + unsafe_put_user(regs->bx, &sc->bx, Efault); + unsafe_put_user(regs->dx, &sc->dx, Efault); + unsafe_put_user(regs->cx, &sc->cx, Efault); + unsafe_put_user(regs->ax, &sc->ax, Efault); +#ifdef CONFIG_X86_64 + unsafe_put_user(regs->r8, &sc->r8, Efault); + unsafe_put_user(regs->r9, &sc->r9, Efault); + unsafe_put_user(regs->r10, &sc->r10, Efault); + unsafe_put_user(regs->r11, &sc->r11, Efault); + unsafe_put_user(regs->r12, &sc->r12, Efault); + unsafe_put_user(regs->r13, &sc->r13, Efault); + unsafe_put_user(regs->r14, &sc->r14, Efault); + unsafe_put_user(regs->r15, &sc->r15, Efault); +#endif /* CONFIG_X86_64 */ + + unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault); + unsafe_put_user(current->thread.error_code, &sc->err, Efault); + unsafe_put_user(regs->ip, &sc->ip, Efault); +#ifdef CONFIG_X86_32 + unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault); + unsafe_put_user(regs->flags, &sc->flags, Efault); + unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault); + unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault); +#else /* !CONFIG_X86_32 */ + unsafe_put_user(regs->flags, &sc->flags, Efault); + unsafe_put_user(regs->cs, &sc->cs, Efault); + unsafe_put_user(0, &sc->gs, Efault); + unsafe_put_user(0, &sc->fs, Efault); + unsafe_put_user(regs->ss, &sc->ss, Efault); +#endif /* CONFIG_X86_32 */ + + unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault); + + /* non-iBCS2 extensions.. */ + unsafe_put_user(mask, &sc->oldmask, Efault); + unsafe_put_user(current->thread.cr2, &sc->cr2, Efault); + return 0; +Efault: + return -EFAULT; +} + +#define unsafe_put_sigcontext(sc, fp, regs, set, label) \ +do { \ + if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0])) \ + goto label; \ +} while(0); + +#define unsafe_put_sigmask(set, frame, label) \ + unsafe_put_user(*(__u64 *)(set), \ + (__u64 __user *)&(frame)->uc.uc_sigmask, \ + label) + +/* + * Set up a signal frame. + */ + +/* x86 ABI requires 16-byte alignment */ +#define FRAME_ALIGNMENT 16UL + +#define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1) + +/* + * Determine which stack to use.. + */ +static unsigned long align_sigframe(unsigned long sp) +{ +#ifdef CONFIG_X86_32 + /* + * Align the stack pointer according to the i386 ABI, + * i.e. so that on function entry ((sp + 4) & 15) == 0. + */ + sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4; +#else /* !CONFIG_X86_32 */ + sp = round_down(sp, FRAME_ALIGNMENT) - 8; +#endif + return sp; +} + +static void __user * +get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, + void __user **fpstate) +{ + /* Default to using normal stack */ + bool nested_altstack = on_sig_stack(regs->sp); + bool entering_altstack = false; + unsigned long math_size = 0; + unsigned long sp = regs->sp; + unsigned long buf_fx = 0; + + /* redzone */ + if (IS_ENABLED(CONFIG_X86_64)) + sp -= 128; + + /* This is the X/Open sanctioned signal stack switching. */ + if (ka->sa.sa_flags & SA_ONSTACK) { + /* + * This checks nested_altstack via sas_ss_flags(). Sensible + * programs use SS_AUTODISARM, which disables that check, and + * programs that don't use SS_AUTODISARM get compatible. + */ + if (sas_ss_flags(sp) == 0) { + sp = current->sas_ss_sp + current->sas_ss_size; + entering_altstack = true; + } + } else if (IS_ENABLED(CONFIG_X86_32) && + !nested_altstack && + regs->ss != __USER_DS && + !(ka->sa.sa_flags & SA_RESTORER) && + ka->sa.sa_restorer) { + /* This is the legacy signal stack switching. */ + sp = (unsigned long) ka->sa.sa_restorer; + entering_altstack = true; + } + + sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32), + &buf_fx, &math_size); + *fpstate = (void __user *)sp; + + sp = align_sigframe(sp - frame_size); + + /* + * If we are on the alternate signal stack and would overflow it, don't. + * Return an always-bogus address instead so we will die with SIGSEGV. + */ + if (unlikely((nested_altstack || entering_altstack) && + !__on_sig_stack(sp))) { + + if (show_unhandled_signals && printk_ratelimit()) + pr_info("%s[%d] overflowed sigaltstack\n", + current->comm, task_pid_nr(current)); + + return (void __user *)-1L; + } + + /* save i387 and extended state */ + if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size)) + return (void __user *)-1L; + + return (void __user *)sp; +} + +#ifdef CONFIG_X86_32 +static const struct { + u16 poplmovl; + u32 val; + u16 int80; +} __attribute__((packed)) retcode = { + 0xb858, /* popl %eax; movl $..., %eax */ + __NR_sigreturn, + 0x80cd, /* int $0x80 */ +}; + +static const struct { + u8 movl; + u32 val; + u16 int80; + u8 pad; +} __attribute__((packed)) rt_retcode = { + 0xb8, /* movl $..., %eax */ + __NR_rt_sigreturn, + 0x80cd, /* int $0x80 */ + 0 +}; + +static int +__setup_frame(int sig, struct ksignal *ksig, sigset_t *set, + struct pt_regs *regs) +{ + struct sigframe __user *frame; + void __user *restorer; + void __user *fp = NULL; + + frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp); + + if (!user_access_begin(frame, sizeof(*frame))) + return -EFAULT; + + unsafe_put_user(sig, &frame->sig, Efault); + unsafe_put_sigcontext(&frame->sc, fp, regs, set, Efault); + unsafe_put_user(set->sig[1], &frame->extramask[0], Efault); + if (current->mm->context.vdso) + restorer = current->mm->context.vdso + + vdso_image_32.sym___kernel_sigreturn; + else + restorer = &frame->retcode; + if (ksig->ka.sa.sa_flags & SA_RESTORER) + restorer = ksig->ka.sa.sa_restorer; + + /* Set up to return from userspace. */ + unsafe_put_user(restorer, &frame->pretcode, Efault); + + /* + * This is popl %eax ; movl $__NR_sigreturn, %eax ; 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 *)&retcode), (u64 *)frame->retcode, Efault); + user_access_end(); + + /* Set up registers for signal handler */ + regs->sp = (unsigned long)frame; + regs->ip = (unsigned long)ksig->ka.sa.sa_handler; + regs->ax = (unsigned long)sig; + regs->dx = 0; + regs->cx = 0; + + regs->ds = __USER_DS; + regs->es = __USER_DS; + regs->ss = __USER_DS; + regs->cs = __USER_CS; + + return 0; + +Efault: + user_access_end(); + return -EFAULT; +} + +static int __setup_rt_frame(int sig, struct ksignal *ksig, + sigset_t *set, struct pt_regs *regs) +{ + struct rt_sigframe __user *frame; + void __user *restorer; + void __user *fp = NULL; + + frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp); + + if (!user_access_begin(frame, sizeof(*frame))) + return -EFAULT; + + 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)) + 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; + 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. + */ + unsafe_put_user(*((u64 *)&rt_retcode), (u64 *)frame->retcode, Efault); + unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault); + unsafe_put_sigmask(set, frame, Efault); + user_access_end(); + + if (copy_siginfo_to_user(&frame->info, &ksig->info)) + return -EFAULT; + + /* Set up registers for signal handler */ + regs->sp = (unsigned long)frame; + regs->ip = (unsigned long)ksig->ka.sa.sa_handler; + regs->ax = (unsigned long)sig; + regs->dx = (unsigned long)&frame->info; + regs->cx = (unsigned long)&frame->uc; + + regs->ds = __USER_DS; + regs->es = __USER_DS; + regs->ss = __USER_DS; + 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) +{ + unsigned long flags; + + if (boot_cpu_has(X86_FEATURE_XSAVE)) + flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS; + else + flags = UC_SIGCONTEXT_SS; + + if (likely(user_64bit_mode(regs))) + flags |= UC_STRICT_RESTORE_SS; + + return flags; +} + +static int __setup_rt_frame(int sig, struct ksignal *ksig, + sigset_t *set, struct pt_regs *regs) +{ + struct rt_sigframe __user *frame; + void __user *fp = NULL; + unsigned long uc_flags; + + /* 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); + uc_flags = frame_uc_flags(regs); + + if (!user_access_begin(frame, sizeof(*frame))) + return -EFAULT; + + /* 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); + unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault); + unsafe_put_sigmask(set, frame, Efault); + user_access_end(); + + if (ksig->ka.sa.sa_flags & SA_SIGINFO) { + if (copy_siginfo_to_user(&frame->info, &ksig->info)) + return -EFAULT; + } + + /* Set up registers for signal handler */ + regs->di = sig; + /* In case the signal handler was declared without prototypes */ + regs->ax = 0; + + /* This also works for non SA_SIGINFO handlers because they expect the + next argument after the signal number on the stack. */ + regs->si = (unsigned long)&frame->info; + regs->dx = (unsigned long)&frame->uc; + regs->ip = (unsigned long) ksig->ka.sa.sa_handler; + + regs->sp = (unsigned long)frame; + + /* + * Set up the CS and SS registers to run signal handlers in + * 64-bit mode, even if the handler happens to be interrupting + * 32-bit or 16-bit code. + * + * SS is subtle. In 64-bit mode, we don't need any particular + * SS descriptor, but we do need SS to be valid. It's possible + * that the old SS is entirely bogus -- this can happen if the + * signal we're trying to deliver is #GP or #SS caused by a bad + * SS value. We also have a compatibility issue here: DOSEMU + * relies on the contents of the SS register indicating the + * SS value at the time of the signal, even though that code in + * DOSEMU predates sigreturn's ability to restore SS. (DOSEMU + * avoids relying on sigreturn to restore SS; instead it uses + * a trampoline.) So we do our best: if the old SS was valid, + * we keep it. Otherwise we replace it. + */ + regs->cs = __USER_CS; + + if (unlikely(regs->ss != __USER_DS)) + force_valid_ss(regs); + + return 0; + +Efault: + user_access_end(); + return -EFAULT; +} +#endif /* CONFIG_X86_32 */ + +#ifdef CONFIG_X86_X32_ABI +static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to, + const struct kernel_siginfo *from) +{ + struct compat_siginfo new; + + copy_siginfo_to_external32(&new, from); + if (from->si_signo == SIGCHLD) { + new._sifields._sigchld_x32._utime = from->si_utime; + new._sifields._sigchld_x32._stime = from->si_stime; + } + if (copy_to_user(to, &new, sizeof(struct compat_siginfo))) + return -EFAULT; + return 0; +} + +int copy_siginfo_to_user32(struct compat_siginfo __user *to, + const struct kernel_siginfo *from) +{ + if (in_x32_syscall()) + return x32_copy_siginfo_to_user(to, from); + return __copy_siginfo_to_user32(to, from); +} +#endif /* CONFIG_X86_X32_ABI */ + +static int x32_setup_rt_frame(struct ksignal *ksig, + compat_sigset_t *set, + struct pt_regs *regs) +{ +#ifdef CONFIG_X86_X32_ABI + struct rt_sigframe_x32 __user *frame; + unsigned long uc_flags; + void __user *restorer; + void __user *fp = NULL; + + if (!(ksig->ka.sa.sa_flags & SA_RESTORER)) + return -EFAULT; + + frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp); + + uc_flags = frame_uc_flags(regs); + + if (!user_access_begin(frame, sizeof(*frame))) + return -EFAULT; + + /* Create the ucontext. */ + unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault); + unsafe_put_user(0, &frame->uc.uc_link, Efault); + unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); + unsafe_put_user(0, &frame->uc.uc__pad0, Efault); + restorer = ksig->ka.sa.sa_restorer; + unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault); + unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault); + unsafe_put_sigmask(set, frame, Efault); + user_access_end(); + + if (ksig->ka.sa.sa_flags & SA_SIGINFO) { + if (x32_copy_siginfo_to_user(&frame->info, &ksig->info)) + return -EFAULT; + } + + /* Set up registers for signal handler */ + regs->sp = (unsigned long) frame; + regs->ip = (unsigned long) ksig->ka.sa.sa_handler; + + /* We use the x32 calling convention here... */ + regs->di = ksig->sig; + regs->si = (unsigned long) &frame->info; + regs->dx = (unsigned long) &frame->uc; + + loadsegment(ds, __USER_DS); + loadsegment(es, __USER_DS); + + regs->cs = __USER_CS; + regs->ss = __USER_DS; +#endif /* CONFIG_X86_X32_ABI */ + + return 0; +#ifdef CONFIG_X86_X32_ABI +Efault: + user_access_end(); + return -EFAULT; +#endif +} + +/* + * Do a signal return; undo the signal stack. + */ +#ifdef CONFIG_X86_32 +SYSCALL_DEFINE0(sigreturn) +{ + struct pt_regs *regs = current_pt_regs(); + struct sigframe __user *frame; + sigset_t set; + + frame = (struct sigframe __user *)(regs->sp - 8); + + if (!access_ok(frame, sizeof(*frame))) + goto badframe; + if (__get_user(set.sig[0], &frame->sc.oldmask) || + __get_user(set.sig[1], &frame->extramask[0])) + goto badframe; + + set_current_blocked(&set); + + /* + * x86_32 has no uc_flags bits relevant to restore_sigcontext. + * Save a few cycles by skipping the __get_user. + */ + if (!restore_sigcontext(regs, &frame->sc, 0)) + goto badframe; + return regs->ax; + +badframe: + signal_fault(regs, frame, "sigreturn"); + + return 0; +} +#endif /* CONFIG_X86_32 */ + +SYSCALL_DEFINE0(rt_sigreturn) +{ + struct pt_regs *regs = current_pt_regs(); + struct rt_sigframe __user *frame; + sigset_t set; + unsigned long uc_flags; + + frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long)); + if (!access_ok(frame, sizeof(*frame))) + goto badframe; + if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask)) + goto badframe; + if (__get_user(uc_flags, &frame->uc.uc_flags)) + goto badframe; + + set_current_blocked(&set); + + if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) + goto badframe; + + if (restore_altstack(&frame->uc.uc_stack)) + goto badframe; + + return regs->ax; + +badframe: + signal_fault(regs, frame, "rt_sigreturn"); + return 0; +} + +/* + * There are four different struct types for signal frame: sigframe_ia32, + * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case + * -- the largest size. It means the size for 64-bit apps is a bit more + * than needed, but this keeps the code simple. + */ +#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32) +#else +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe) +#endif + +/* + * The FP state frame contains an XSAVE buffer which must be 64-byte aligned. + * If a signal frame starts at an unaligned address, extra space is required. + * This is the max alignment padding, conservatively. + */ +#define MAX_XSAVE_PADDING 63UL + +/* + * The frame data is composed of the following areas and laid out as: + * + * ------------------------- + * | alignment padding | + * ------------------------- + * | (f)xsave frame | + * ------------------------- + * | fsave header | + * ------------------------- + * | alignment padding | + * ------------------------- + * | siginfo + ucontext | + * ------------------------- + */ + +/* max_frame_size tells userspace the worst case signal stack size. */ +static unsigned long __ro_after_init max_frame_size; +static unsigned int __ro_after_init fpu_default_state_size; + +static int __init init_sigframe_size(void) +{ + fpu_default_state_size = fpu__get_fpstate_size(); + + max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING; + + max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING; + + /* Userspace expects an aligned size. */ + max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT); + + pr_info("max sigframe size: %lu\n", max_frame_size); + return 0; +} +early_initcall(init_sigframe_size); + +unsigned long get_sigframe_size(void) +{ + return max_frame_size; +} + +static inline int is_ia32_compat_frame(struct ksignal *ksig) +{ + return IS_ENABLED(CONFIG_IA32_EMULATION) && + ksig->ka.sa.sa_flags & SA_IA32_ABI; +} + +static inline int is_ia32_frame(struct ksignal *ksig) +{ + return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig); +} + +static inline int is_x32_frame(struct ksignal *ksig) +{ + return IS_ENABLED(CONFIG_X86_X32_ABI) && + ksig->ka.sa.sa_flags & SA_X32_ABI; +} + +static int +setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs) +{ + int usig = ksig->sig; + sigset_t *set = sigmask_to_save(); + compat_sigset_t *cset = (compat_sigset_t *) set; + + /* Perform fixup for the pre-signal frame. */ + rseq_signal_deliver(ksig, regs); + + /* Set up the stack frame */ + if (is_ia32_frame(ksig)) { + if (ksig->ka.sa.sa_flags & SA_SIGINFO) + return ia32_setup_rt_frame(usig, ksig, cset, regs); + else + return ia32_setup_frame(usig, ksig, cset, regs); + } else if (is_x32_frame(ksig)) { + return x32_setup_rt_frame(ksig, cset, regs); + } else { + return __setup_rt_frame(ksig->sig, ksig, set, regs); + } +} + +static void +handle_signal(struct ksignal *ksig, struct pt_regs *regs) +{ + bool stepping, failed; + struct fpu *fpu = ¤t->thread.fpu; + + if (v8086_mode(regs)) + save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL); + + /* Are we from a system call? */ + if (syscall_get_nr(current, regs) != -1) { + /* If so, check system call restarting.. */ + switch (syscall_get_error(current, regs)) { + case -ERESTART_RESTARTBLOCK: + case -ERESTARTNOHAND: + regs->ax = -EINTR; + break; + + case -ERESTARTSYS: + if (!(ksig->ka.sa.sa_flags & SA_RESTART)) { + regs->ax = -EINTR; + break; + } + fallthrough; + case -ERESTARTNOINTR: + regs->ax = regs->orig_ax; + regs->ip -= 2; + break; + } + } + + /* + * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now + * so that register information in the sigcontext is correct and + * then notify the tracer before entering the signal handler. + */ + stepping = test_thread_flag(TIF_SINGLESTEP); + if (stepping) + user_disable_single_step(current); + + failed = (setup_rt_frame(ksig, regs) < 0); + if (!failed) { + /* + * Clear the direction flag as per the ABI for function entry. + * + * Clear RF when entering the signal handler, because + * it might disable possible debug exception from the + * signal handler. + * + * Clear TF for the case when it wasn't set by debugger to + * avoid the recursive send_sigtrap() in SIGTRAP handler. + */ + regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF); + /* + * Ensure the signal handler starts with the new fpu state. + */ + fpu__clear_user_states(fpu); + } + signal_setup_done(failed, ksig, stepping); +} + +static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs) +{ +#ifdef CONFIG_IA32_EMULATION + if (current->restart_block.arch_data & TS_COMPAT) + return __NR_ia32_restart_syscall; +#endif +#ifdef CONFIG_X86_X32_ABI + return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT); +#else + return __NR_restart_syscall; +#endif +} + +/* + * Note that 'init' is a special process: it doesn't get signals it doesn't + * want to handle. Thus you cannot kill init even with a SIGKILL even by + * mistake. + */ +void arch_do_signal_or_restart(struct pt_regs *regs) +{ + struct ksignal ksig; + + if (get_signal(&ksig)) { + /* Whee! Actually deliver the signal. */ + handle_signal(&ksig, regs); + return; + } + + /* Did we come from a system call? */ + if (syscall_get_nr(current, regs) != -1) { + /* Restart the system call - no handlers present */ + switch (syscall_get_error(current, regs)) { + case -ERESTARTNOHAND: + case -ERESTARTSYS: + case -ERESTARTNOINTR: + regs->ax = regs->orig_ax; + regs->ip -= 2; + break; + + case -ERESTART_RESTARTBLOCK: + regs->ax = get_nr_restart_syscall(regs); + regs->ip -= 2; + break; + } + } + + /* + * If there's no signal to deliver, we just put the saved sigmask + * back. + */ + restore_saved_sigmask(); +} + +void signal_fault(struct pt_regs *regs, void __user *frame, char *where) +{ + struct task_struct *me = current; + + if (show_unhandled_signals && printk_ratelimit()) { + printk("%s" + "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx", + task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG, + me->comm, me->pid, where, frame, + regs->ip, regs->sp, regs->orig_ax); + print_vma_addr(KERN_CONT " in ", regs->ip); + pr_cont("\n"); + } + + force_sig(SIGSEGV); +} + +#ifdef CONFIG_DYNAMIC_SIGFRAME +#ifdef CONFIG_STRICT_SIGALTSTACK_SIZE +static bool strict_sigaltstack_size __ro_after_init = true; +#else +static bool strict_sigaltstack_size __ro_after_init = false; +#endif + +static int __init strict_sas_size(char *arg) +{ + return kstrtobool(arg, &strict_sigaltstack_size) == 0; +} +__setup("strict_sas_size", strict_sas_size); + +/* + * MINSIGSTKSZ is 2048 and can't be changed despite the fact that AVX512 + * exceeds that size already. As such programs might never use the + * sigaltstack they just continued to work. While always checking against + * the real size would be correct, this might be considered a regression. + * + * Therefore avoid the sanity check, unless enforced by kernel + * configuration or command line option. + * + * When dynamic FPU features are supported, the check is also enforced when + * the task has permissions to use dynamic features. Tasks which have no + * permission are checked against the size of the non-dynamic feature set + * if strict checking is enabled. This avoids forcing all tasks on the + * system to allocate large sigaltstacks even if they are never going + * to use a dynamic feature. As this is serialized via sighand::siglock + * any permission request for a dynamic feature either happened already + * or will see the newly install sigaltstack size in the permission checks. + */ +bool sigaltstack_size_valid(size_t ss_size) +{ + unsigned long fsize = max_frame_size - fpu_default_state_size; + u64 mask; + + lockdep_assert_held(¤t->sighand->siglock); + + if (!fpu_state_size_dynamic() && !strict_sigaltstack_size) + return true; + + fsize += current->group_leader->thread.fpu.perm.__user_state_size; + if (likely(ss_size > fsize)) + return true; + + if (strict_sigaltstack_size) + return ss_size > fsize; + + mask = current->group_leader->thread.fpu.perm.__state_perm; + if (mask & XFEATURE_MASK_USER_DYNAMIC) + return ss_size > fsize; + + return true; +} +#endif /* CONFIG_DYNAMIC_SIGFRAME */ + +#ifdef CONFIG_X86_X32_ABI +COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn) +{ + struct pt_regs *regs = current_pt_regs(); + struct rt_sigframe_x32 __user *frame; + sigset_t set; + unsigned long uc_flags; + + frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8); + + if (!access_ok(frame, sizeof(*frame))) + goto badframe; + if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask)) + goto badframe; + if (__get_user(uc_flags, &frame->uc.uc_flags)) + goto badframe; + + set_current_blocked(&set); + + if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) + goto badframe; + + if (compat_restore_altstack(&frame->uc.uc_stack)) + goto badframe; + + return regs->ax; + +badframe: + signal_fault(regs, frame, "x32 rt_sigreturn"); + return 0; +} +#endif |