fixup_umip_exception() will be called from do_general_protection. If the former returns false, the latter will issue a SIGSEGV with SEND_SIG_PRIV. However, when emulation is successful but the emulated result cannot be copied to user space memory, it is more accurate to issue a SIGSEGV with SEGV_MAPERR with the offending address. A new function is inspired in force_sig_info_fault is introduced to model the page fault.
Cc: Andy Lutomirski <[email protected]> Cc: Andrew Morton <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Chen Yucong <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: Huang Rui <[email protected]> Cc: Jiri Slaby <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Michael S. Tsirkin <[email protected]> Cc: Paul Gortmaker <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Ravi V. Shankar <[email protected]> Cc: Shuah Khan <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Tony Luck <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Liang Z. Li <[email protected]> Cc: Alexandre Julliard <[email protected]> Cc: Stas Sergeev <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Ricardo Neri <[email protected]> --- arch/x86/kernel/umip.c | 45 +++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 43 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c index c7c5795..ff7366a 100644 --- a/arch/x86/kernel/umip.c +++ b/arch/x86/kernel/umip.c @@ -148,6 +148,41 @@ static int __emulate_umip_insn(struct insn *insn, enum umip_insn umip_inst, } /** + * __force_sig_info_umip_fault() - Force a SIGSEGV with SEGV_MAPERR + * @address: Address that caused the signal + * @regs: Register set containing the instruction pointer + * + * Force a SIGSEGV signal with SEGV_MAPERR as the error code. This function is + * intended to be used to provide a segmentation fault when the result of the + * UMIP emulation could not be copied to the user space memory. + * + * Return: none + */ +static void __force_sig_info_umip_fault(void __user *address, + struct pt_regs *regs) +{ + siginfo_t info; + struct task_struct *tsk = current; + + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV)) { + printk_ratelimited("%s[%d] umip emulation segfault ip:%lx sp:%lx error:%x in %lx\n", + tsk->comm, task_pid_nr(tsk), regs->ip, + regs->sp, X86_PF_USER | X86_PF_WRITE, + regs->ip); + } + + tsk->thread.cr2 = (unsigned long)address; + tsk->thread.error_code = X86_PF_USER | X86_PF_WRITE; + tsk->thread.trap_nr = X86_TRAP_PF; + + info.si_signo = SIGSEGV; + info.si_errno = 0; + info.si_code = SEGV_MAPERR; + info.si_addr = address; + force_sig_info(SIGSEGV, &info, tsk); +} + +/** * fixup_umip_exception() - Fixup #GP faults caused by UMIP * @regs: Registers as saved when entering the #GP trap * @@ -235,8 +270,14 @@ bool fixup_umip_exception(struct pt_regs *regs) if ((unsigned long)uaddr == -1L) return false; nr_copied = copy_to_user(uaddr, dummy_data, dummy_data_size); - if (nr_copied > 0) - return false; + if (nr_copied > 0) { + /* + * If copy fails, send a signal and tell caller that + * fault was fixed up + */ + __force_sig_info_umip_fault(uaddr, regs); + return true; + } } /* increase IP to let the program keep going */ -- 2.9.3
