diff options
Diffstat (limited to 'arch/x86/kernel/signal.c')
| -rw-r--r-- | arch/x86/kernel/signal.c | 808 |
1 files changed, 179 insertions, 629 deletions
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 399f97abee02..2404233336ab 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -15,9 +15,9 @@ #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/tracehook.h> #include <linux/unistd.h> #include <linux/stddef.h> #include <linux/personality.h> @@ -25,680 +25,229 @@ #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 <linux/rseq.h> #include <asm/processor.h> #include <asm/ucontext.h> -#include <asm/fpu/internal.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> -#endif /* CONFIG_X86_64 */ - #include <asm/syscall.h> #include <asm/sigframe.h> #include <asm/signal.h> +#include <asm/shstk.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) +static inline int is_ia32_compat_frame(struct ksignal *ksig) { - 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; + return IS_ENABLED(CONFIG_IA32_EMULATION) && + ksig->ka.sa.sa_flags & SA_IA32_ABI; } -# define CONTEXT_COPY_SIZE offsetof(struct sigcontext, reserved1) -#else -# define CONTEXT_COPY_SIZE sizeof(struct sigcontext) -#endif -static int restore_sigcontext(struct pt_regs *regs, - struct sigcontext __user *usc, - unsigned long uc_flags) +static inline int is_ia32_frame(struct ksignal *ksig) { - 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 -EFAULT; - -#ifdef CONFIG_X86_32 - set_user_gs(regs, 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)); + return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig); } -static __always_inline int -__unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate, - struct pt_regs *regs, unsigned long mask) +static inline int is_x32_frame(struct ksignal *ksig) { -#ifdef CONFIG_X86_32 - unsafe_put_user(get_user_gs(regs), - (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; + return IS_ENABLED(CONFIG_X86_X32_ABI) && + ksig->ka.sa.sa_flags & SA_X32_ABI; } -#define unsafe_put_sigcontext(sc, fp, regs, set, label) \ -do { \ - if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0])) \ - goto label; \ -} while(0); +/* + * Enable all pkeys temporarily, so as to ensure that both the current + * execution stack as well as the alternate signal stack are writeable. + * The application can use any of the available pkeys to protect the + * alternate signal stack, and we don't know which one it is, so enable + * all. The PKRU register will be reset to init_pkru later in the flow, + * in fpu__clear_user_states(), and it is the application's responsibility + * to enable the appropriate pkey as the first step in the signal handler + * so that the handler does not segfault. + */ +static inline u32 sig_prepare_pkru(void) +{ + u32 orig_pkru = read_pkru(); -#define unsafe_put_sigmask(set, frame, label) \ - unsafe_put_user(*(__u64 *)(set), \ - (__u64 __user *)&(frame)->uc.uc_sigmask, \ - label) + write_pkru(0); + return orig_pkru; +} /* * 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) & -16ul) - 4; -#else /* !CONFIG_X86_32 */ - sp = round_down(sp, 16) - 8; -#endif - return sp; -} - -static void __user * -get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, +void __user * +get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size, void __user **fpstate) { + struct k_sigaction *ka = &ksig->ka; + int ia32_frame = is_ia32_frame(ksig); /* 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; - int onsigstack = on_sig_stack(sp); - int ret; + u32 pkru; /* redzone */ - if (IS_ENABLED(CONFIG_X86_64)) + if (!ia32_frame) sp -= 128; /* This is the X/Open sanctioned signal stack switching. */ if (ka->sa.sa_flags & SA_ONSTACK) { - if (sas_ss_flags(sp) == 0) + /* + * 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; - } else if (IS_ENABLED(CONFIG_X86_32) && - !onsigstack && + entering_altstack = true; + } + } else if (ia32_frame && + !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); + sp = fpu__alloc_mathframe(sp, ia32_frame, &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 (onsigstack && !likely(on_sig_stack(sp))) - return (void __user *)-1L; + sp -= frame_size; - /* save i387 and extended state */ - ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size); - if (ret < 0) - 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); + if (ia32_frame) + /* + * 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 - 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); + sp = round_down(sp, FRAME_ALIGNMENT) - 8; /* - * 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. + * 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. */ - 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 (unlikely((nested_altstack || entering_altstack) && + !__on_sig_stack(sp))) { - if (boot_cpu_has(X86_FEATURE_XSAVE)) - flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS; - else - flags = UC_SIGCONTEXT_SS; + if (show_unhandled_signals && printk_ratelimit()) + pr_info("%s[%d] overflowed sigaltstack\n", + current->comm, task_pid_nr(current)); - 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; + return (void __user *)-1L; } - /* 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 compatbility 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; + /* Update PKRU to enable access to the alternate signal stack. */ + pkru = sig_prepare_pkru(); + /* save i387 and extended state */ + if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size, pkru)) { + /* + * Restore PKRU to the original, user-defined value; disable + * extra pkeys enabled for the alternate signal stack, if any. + */ + write_pkru(pkru); + return (void __user *)-1L; } - 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); + return (void __user *)sp; } -#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; +/* + * 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 -} /* - * Do a signal return; undo the signal stack. + * 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. */ -#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); +#define MAX_XSAVE_PADDING 63UL - 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"); +/* + * The frame data is composed of the following areas and laid out as: + * + * ------------------------- + * | alignment padding | + * ------------------------- + * | (f)xsave frame | + * ------------------------- + * | fsave header | + * ------------------------- + * | alignment padding | + * ------------------------- + * | siginfo + ucontext | + * ------------------------- + */ - return 0; -} -#endif /* CONFIG_X86_32 */ +/* 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; -SYSCALL_DEFINE0(rt_sigreturn) +static int __init init_sigframe_size(void) { - 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; + fpu_default_state_size = fpu__get_fpstate_size(); - set_current_blocked(&set); + max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING; - if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) - goto badframe; + max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING; - if (restore_altstack(&frame->uc.uc_stack)) - goto badframe; + /* Userspace expects an aligned size. */ + max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT); - return regs->ax; - -badframe: - signal_fault(regs, frame, "rt_sigreturn"); + pr_info("max sigframe size: %lu\n", max_frame_size); return 0; } +early_initcall(init_sigframe_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) +unsigned long get_sigframe_size(void) { - 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; + return max_frame_size; } 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); + return ia32_setup_rt_frame(ksig, regs); else - return ia32_setup_frame(usig, ksig, cset, regs); + return ia32_setup_frame(ksig, regs); } else if (is_x32_frame(ksig)) { - return x32_setup_rt_frame(ksig, cset, regs); + return x32_setup_rt_frame(ksig, regs); } else { - return __setup_rt_frame(ksig->sig, ksig, set, regs); + return x64_setup_rt_frame(ksig, regs); } } @@ -706,13 +255,13 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) { bool stepping, failed; - struct fpu *fpu = ¤t->thread.fpu; + struct fpu *fpu = x86_task_fpu(current); 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) >= 0) { + if (syscall_get_nr(current, regs) != -1) { /* If so, check system call restarting.. */ switch (syscall_get_error(current, regs)) { case -ERESTART_RESTARTBLOCK: @@ -725,7 +274,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs) regs->ax = -EINTR; break; } - /* fallthrough */ + fallthrough; case -ERESTARTNOINTR: regs->ax = regs->orig_ax; regs->ip -= 2; @@ -765,30 +314,8 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs) static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs) { - /* - * This function is fundamentally broken as currently - * implemented. - * - * The idea is that we want to trigger a call to the - * restart_block() syscall and that we want in_ia32_syscall(), - * in_x32_syscall(), etc. to match whatever they were in the - * syscall being restarted. We assume that the syscall - * instruction at (regs->ip - 2) matches whatever syscall - * instruction we used to enter in the first place. - * - * The problem is that we can get here when ptrace pokes - * syscall-like values into regs even if we're not in a syscall - * at all. - * - * For now, we maintain historical behavior and guess based on - * stored state. We could do better by saving the actual - * syscall arch in restart_block or (with caveats on x32) by - * checking if regs->ip points to 'int $0x80'. The current - * behavior is incorrect if a tracer has a different bitness - * than the tracee. - */ #ifdef CONFIG_IA32_EMULATION - if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED)) + if (current->restart_block.arch_data & TS_COMPAT) return __NR_ia32_restart_syscall; #endif #ifdef CONFIG_X86_X32_ABI @@ -803,7 +330,7 @@ static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs) * want to handle. Thus you cannot kill init even with a SIGKILL even by * mistake. */ -void do_signal(struct pt_regs *regs) +void arch_do_signal_or_restart(struct pt_regs *regs) { struct ksignal ksig; @@ -814,7 +341,7 @@ void do_signal(struct pt_regs *regs) } /* Did we come from a system call? */ - if (syscall_get_nr(current, regs) >= 0) { + if (syscall_get_nr(current, regs) != -1) { /* Restart the system call - no handlers present */ switch (syscall_get_error(current, regs)) { case -ERESTARTNOHAND: @@ -855,35 +382,58 @@ void signal_fault(struct pt_regs *regs, void __user *frame, char *where) force_sig(SIGSEGV); } -#ifdef CONFIG_X86_X32_ABI -COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn) +#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) { - struct pt_regs *regs = current_pt_regs(); - struct rt_sigframe_x32 __user *frame; - sigset_t set; - unsigned long uc_flags; + return kstrtobool(arg, &strict_sigaltstack_size) == 0; +} +__setup("strict_sas_size", strict_sas_size); - frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8); +/* + * 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; - 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; + lockdep_assert_held(¤t->sighand->siglock); - set_current_blocked(&set); + if (!fpu_state_size_dynamic() && !strict_sigaltstack_size) + return true; - if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) - goto badframe; + fsize += x86_task_fpu(current->group_leader)->perm.__user_state_size; + if (likely(ss_size > fsize)) + return true; - if (compat_restore_altstack(&frame->uc.uc_stack)) - goto badframe; + if (strict_sigaltstack_size) + return ss_size > fsize; - return regs->ax; + mask = x86_task_fpu(current->group_leader)->perm.__state_perm; + if (mask & XFEATURE_MASK_USER_DYNAMIC) + return ss_size > fsize; -badframe: - signal_fault(regs, frame, "x32 rt_sigreturn"); - return 0; + return true; } -#endif +#endif /* CONFIG_DYNAMIC_SIGFRAME */ |