From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from NAM03-DM3-obe.outbound.protection.outlook.com (mail-dm3nam03on0126.outbound.protection.outlook.com [104.47.41.126]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 404h3k0lYSzF0my for ; Tue, 20 Mar 2018 03:14:57 +1100 (AEDT) From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: "Eric W. Biederman" , Paul Mackerras , Kumar Gala , Michael Ellerman , Benjamin Herrenschmidt , "linuxppc-dev@lists.ozlabs.org" , Sasha Levin Subject: [PATCH AUTOSEL for 3.18 101/102] signal/powerpc: Document conflicts with SI_USER and SIGFPE and SIGTRAP Date: Mon, 19 Mar 2018 16:13:40 +0000 Message-ID: <20180319161117.17833-101-alexander.levin@microsoft.com> References: <20180319161117.17833-1-alexander.levin@microsoft.com> In-Reply-To: <20180319161117.17833-1-alexander.levin@microsoft.com> Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: "Eric W. Biederman" [ Upstream commit cf4674c46c66e45f238f8f7e81af2a444b970c0a ] 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 =3D=3D 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 ex= ceptions.") History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.= git Signed-off-by: "Eric W. Biederman" Signed-off-by: Sasha Levin --- 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 ccce3ef5cd86..9c437eaf7c21 100644 --- a/arch/powerpc/include/uapi/asm/siginfo.h +++ b/arch/powerpc/include/uapi/asm/siginfo.h @@ -17,4 +17,19 @@ #undef NSIGTRAP #define NSIGTRAP 4 =20 +/* + * 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 0dc43f9932cf..6cc0280a8ae0 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -769,7 +769,7 @@ void unknown_exception(struct pt_regs *regs) printk("Bad trap at PC: %lx, SR: %lx, vector=3D%lx\n", regs->nip, regs->msr, regs->trap); =20 - _exception(SIGTRAP, regs, 0, 0); + _exception(SIGTRAP, regs, TRAP_FIXME, 0); =20 exception_exit(prev_state); } @@ -791,7 +791,7 @@ void instruction_breakpoint_exception(struct pt_regs *r= egs) =20 void RunModeException(struct pt_regs *regs) { - _exception(SIGTRAP, regs, 0, 0); + _exception(SIGTRAP, regs, TRAP_FIXME, 0); } =20 void __kprobes single_step_exception(struct pt_regs *regs) @@ -826,7 +826,7 @@ static void emulate_single_step(struct pt_regs *regs) =20 static inline int __parse_fpscr(unsigned long fpscr) { - int ret =3D 0; + int ret =3D FPE_FIXME; =20 /* Invalid operation */ if ((fpscr & FPSCR_VE) && (fpscr & FPSCR_VX)) @@ -1742,7 +1742,7 @@ void SPEFloatingPointException(struct pt_regs *regs) extern int do_spe_mathemu(struct pt_regs *regs); unsigned long spefscr; int fpexc_mode; - int code =3D 0; + int code =3D FPE_FIXME; int err; =20 flush_spe_to_thread(current); @@ -1811,7 +1811,7 @@ void SPEFloatingPointRoundException(struct pt_regs *r= egs) 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; } } --=20 2.14.1