diff options
Diffstat (limited to 'arch/x86/kernel/signal.c')
| -rw-r--r-- | arch/x86/kernel/signal.c | 48 |
1 files changed, 21 insertions, 27 deletions
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 8eb7193e158d..026ce06a24c0 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -241,10 +241,11 @@ 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; - int onsigstack = on_sig_stack(sp); int ret; /* redzone */ @@ -253,15 +254,23 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, /* 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; + entering_altstack = true; + } } else if (IS_ENABLED(CONFIG_X86_32) && - !onsigstack && + !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), @@ -274,8 +283,15 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t 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))) + 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 */ ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size); @@ -770,30 +786,8 @@ 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_thread_info()->status & TS_COMPAT_RESTART) return __NR_ia32_restart_syscall; #endif #ifdef CONFIG_X86_X32_ABI |