Messages in this thread | | | Date | Fri, 31 Oct 2014 10:12:07 +0800 | From | Ren Qiaowei <> | Subject | Re: [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound violation information |
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On 10/31/2014 06:38 AM, Dave Hansen wrote: >> +void do_mpx_bounds(struct pt_regs *regs, siginfo_t *info, >> + struct xsave_struct *xsave_buf) >> +{ >> + struct mpx_insn insn; >> + uint8_t bndregno; >> + unsigned long addr_vio; >> + >> + addr_vio = mpx_insn_decode(&insn, regs); >> + >> + bndregno = X86_MODRM_REG(insn.modrm.value); >> + if (bndregno > 3) >> + return; >> + >> + /* Note: the upper 32 bits are ignored in 32-bit mode. */ >> + info->si_lower = (void __user *)(unsigned long) >> + (xsave_buf->bndregs.bndregs[2*bndregno]); >> + info->si_upper = (void __user *)(unsigned long) >> + (~xsave_buf->bndregs.bndregs[2*bndregno+1]); >> + info->si_addr_lsb = 0; >> + info->si_signo = SIGSEGV; >> + info->si_errno = 0; >> + info->si_code = SEGV_BNDERR; >> + info->si_addr = (void __user *)addr_vio; >> +} >> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c >> index 611b6ec..b2a916b 100644 >> --- a/arch/x86/kernel/traps.c >> +++ b/arch/x86/kernel/traps.c >> @@ -284,6 +284,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) >> unsigned long status; >> struct xsave_struct *xsave_buf; >> struct task_struct *tsk = current; >> + siginfo_t info; >> >> prev_state = exception_enter(); >> if (notify_die(DIE_TRAP, "bounds", regs, error_code, >> @@ -316,6 +317,11 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) >> break; >> >> case 1: /* Bound violation. */ >> + do_mpx_bounds(regs, &info, xsave_buf); >> + do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, >> + error_code, &info); >> + break; >> + >> case 0: /* No exception caused by Intel MPX operations. */ >> do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, NULL); >> break; >> > > So, siginfo is stack-allocarted here. do_mpx_bounds() can error out if > it sees an invalid bndregno. We still send the signal with the &info > whether or not we filled the 'info' in do_mpx_bounds(). > > Can't this leak some kernel stack out in the 'info'? >
This should check the return value of do_mpx_bounds and should be fixed.
Thanks, Qiaowei
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