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Date: Tue, 3 Oct 2017 20:54:28 -0700 From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> To: Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de> Cc: Peter Zijlstra <peterz@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Brian Gerst <brgerst@...il.com>, Chris Metcalf <cmetcalf@...lanox.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Paolo Bonzini <pbonzini@...hat.com>, Liang Z Li <liang.z.li@...el.com>, Masami Hiramatsu <mhiramat@...nel.org>, Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>, Jonathan Corbet <corbet@....net>, "Michael S. Tsirkin" <mst@...hat.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, Vlastimil Babka <vbabka@...e.cz>, Chen Yucong <slaoub@...il.com>, "Ravi V. Shankar" <ravi.v.shankar@...el.com>, Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org, x86@...nel.org, ricardo.neri@...el.com, Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, Fenghua Yu <fenghua.yu@...el.com>, Tony Luck <tony.luck@...el.com> Subject: [PATCH v9 25/29] x86/umip: Force a page fault when unable to copy emulated result to user 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, inspired in force_sig_info_fault(), is introduced to model the page fault. Cc: Andy Lutomirski <luto@...nel.org> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: H. Peter Anvin <hpa@...or.com> Cc: Borislav Petkov <bp@...e.de> Cc: Brian Gerst <brgerst@...il.com> Cc: Chen Yucong <slaoub@...il.com> Cc: Chris Metcalf <cmetcalf@...lanox.com> Cc: Dave Hansen <dave.hansen@...ux.intel.com> Cc: Fenghua Yu <fenghua.yu@...el.com> Cc: Huang Rui <ray.huang@....com> Cc: Jiri Slaby <jslaby@...e.cz> Cc: Jonathan Corbet <corbet@....net> Cc: Michael S. Tsirkin <mst@...hat.com> Cc: Paul Gortmaker <paul.gortmaker@...driver.com> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Ravi V. Shankar <ravi.v.shankar@...el.com> Cc: Shuah Khan <shuah@...nel.org> Cc: Vlastimil Babka <vbabka@...e.cz> Cc: Tony Luck <tony.luck@...el.com> Cc: Paolo Bonzini <pbonzini@...hat.com> Cc: x86@...nel.org Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> --- 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 1f338cb..6d07eb5 100644 --- a/arch/x86/kernel/umip.c +++ b/arch/x86/kernel/umip.c @@ -187,6 +187,41 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst, } /** + * force_sig_info_umip_fault() - Force a SIGSEGV with SEGV_MAPERR + * @addr: 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. + * + * Returns: none + */ +static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs) +{ + siginfo_t info; + struct task_struct *tsk = current; + + tsk->thread.cr2 = (unsigned long)addr; + 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 = addr; + force_sig_info(SIGSEGV, &info, tsk); + + if (!(show_unhandled_signals && unhandled_signal(tsk, SIGSEGV))) + return; + + pr_err_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); +} + +/** * fixup_umip_exception() - Fixup #GP faults caused by UMIP * @regs: Registers as saved when entering the #GP trap * @@ -299,8 +334,14 @@ bool fixup_umip_exception(struct pt_regs *regs) 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 */ -- 2.7.4
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