Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933794AbeALBBk (ORCPT + 1 other); Thu, 11 Jan 2018 20:01:40 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:35545 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933242AbeALBBf (ORCPT ); Thu, 11 Jan 2018 20:01:35 -0500 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: Al Viro , Oleg Nesterov , linux-arch@vger.kernel.org, "Eric W. Biederman" , Paul Mackerras , Kumar Gala , Michael Ellerman , Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org Date: Thu, 11 Jan 2018 18:59:35 -0600 Message-Id: <20180112005940.23279-6-ebiederm@xmission.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <87373b6ghs.fsf@xmission.com> References: <87373b6ghs.fsf@xmission.com> X-XM-SPF: eid=1eZnit-00053y-0M;;;mid=<20180112005940.23279-6-ebiederm@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=97.121.73.102;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+lgMwTBNYIZ3+JGn7yd0TLrv+B1N2S4lI= X-SA-Exim-Connect-IP: 97.121.73.102 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 06/11] signal/powerpc: Document conflicts with SI_USER and SIGFPE and SIGTRAP X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Setting si_code to 0 results in a userspace seeing an si_code of 0. This is the same si_code as SI_USER. Posix and common sense requires that SI_USER not be a signal specific si_code. As such this use of 0 for the si_code is a pretty horribly broken ABI. Further use of si_code == 0 guaranteed that copy_siginfo_to_user saw a value of __SI_KILL and now sees a value of SIL_KILL with the result that uid and pid fields are copied and which might copying the si_addr field by accident but certainly not by design. Making this a very flakey implementation. Utilizing FPE_FIXME and TRAP_FIXME, siginfo_layout() will now return SIL_FAULT and the appropriate fields will be reliably copied. Possible ABI fixes includee: - Send the signal without siginfo - Don't generate a signal - Possibly assign and use an appropriate si_code - Don't handle cases which can't happen Cc: Paul Mackerras Cc: Kumar Gala Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: linuxppc-dev@lists.ozlabs.org Ref: 9bad068c24d7 ("[PATCH] ppc32: support for e500 and 85xx") Ref: 0ed70f6105ef ("PPC32: Provide proper siginfo information on various exceptions.") History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Signed-off-by: "Eric W. Biederman" --- arch/powerpc/include/uapi/asm/siginfo.h | 15 +++++++++++++++ arch/powerpc/kernel/traps.c | 10 +++++----- 2 files changed, 20 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/include/uapi/asm/siginfo.h b/arch/powerpc/include/uapi/asm/siginfo.h index 1a691141e49f..444ca6c9989a 100644 --- a/arch/powerpc/include/uapi/asm/siginfo.h +++ b/arch/powerpc/include/uapi/asm/siginfo.h @@ -18,4 +18,19 @@ #undef NSIGTRAP #define NSIGTRAP 4 +/* + * SIGFPE si_codes + */ +#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + +/* + * SIGTRAP si_codes + */ +#ifdef __KERNEL__ +#define TRAP_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + + #endif /* _ASM_POWERPC_SIGINFO_H */ diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index f3eb61be0d30..f2e6e1838952 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -917,7 +917,7 @@ void unknown_exception(struct pt_regs *regs) printk("Bad trap at PC: %lx, SR: %lx, vector=%lx\n", regs->nip, regs->msr, regs->trap); - _exception(SIGTRAP, regs, 0, 0); + _exception(SIGTRAP, regs, TRAP_FIXME, 0); exception_exit(prev_state); } @@ -939,7 +939,7 @@ void instruction_breakpoint_exception(struct pt_regs *regs) void RunModeException(struct pt_regs *regs) { - _exception(SIGTRAP, regs, 0, 0); + _exception(SIGTRAP, regs, TRAP_FIXME, 0); } void single_step_exception(struct pt_regs *regs) @@ -978,7 +978,7 @@ static void emulate_single_step(struct pt_regs *regs) static inline int __parse_fpscr(unsigned long fpscr) { - int ret = 0; + int ret = FPE_FIXME; /* Invalid operation */ if ((fpscr & FPSCR_VE) && (fpscr & FPSCR_VX)) @@ -1929,7 +1929,7 @@ void SPEFloatingPointException(struct pt_regs *regs) extern int do_spe_mathemu(struct pt_regs *regs); unsigned long spefscr; int fpexc_mode; - int code = 0; + int code = FPE_FIXME; int err; flush_spe_to_thread(current); @@ -1998,7 +1998,7 @@ void SPEFloatingPointRoundException(struct pt_regs *regs) printk(KERN_ERR "unrecognized spe instruction " "in %s at %lx\n", current->comm, regs->nip); } else { - _exception(SIGFPE, regs, 0, regs->nip); + _exception(SIGFPE, regs, FPE_FIXME, regs->nip); return; } } -- 2.14.1