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Mon, 19 Mar 2018 16:06:38 +0000 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: [PATCH AUTOSEL for 4.9 280/281] signal/arm: Document conflicts with SI_USER and SIGFPE Thread-Topic: [PATCH AUTOSEL for 4.9 280/281] signal/arm: Document conflicts with SI_USER and SIGFPE Thread-Index: AQHTv5vRBysmsmFMuUKl8/UCI7sg6Q== Date: Mon, 19 Mar 2018 16:03:27 +0000 Message-ID: <20180319155742.13731-280-alexander.levin@microsoft.com> References: <20180319155742.13731-1-alexander.levin@microsoft.com> In-Reply-To: <20180319155742.13731-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; DM5PR2101MB0728; 7:Hdei54+34ViPe+In66h2tC+Q8QdhXYgvJdCQErSjUZM41sCSTs/unsE26rN9A43YWdE34Kj+4vNzACzhrWnHHZ9j9FtxM6vjLxSToiOBBZUeDYrC2Y5Q7u3A+jzjZyGEhDQQ3O5WjTI6ik+F2GvVUWLe6WRweDCFtxviqxeuD1k+BPshLU82m6aP7C49VPhNmlxAH4LgNQAxZ8aTfgL144MdkVBIn6Az/HNN+t9j3ETBamHANEvYlIiW74hq5Zpv; 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Biederman" , "linux-arm-kernel@lists.infradead.org" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP From: "Eric W. Biederman" [ Upstream commit 7771c66457004977b616bab785209f49d164f527 ] 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, 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: Russell King Cc: linux-arm-kernel@lists.infradead.org Ref: 451436b7bbb2 ("[ARM] Add support code for ARM hardware vector floating point") 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/arm/include/uapi/asm/siginfo.h | 13 +++++++++++++ arch/arm/vfp/vfpmodule.c | 2 +- 2 files changed, 14 insertions(+), 1 deletion(-) create mode 100644 arch/arm/include/uapi/asm/siginfo.h diff --git a/arch/arm/include/uapi/asm/siginfo.h b/arch/arm/include/uapi/asm/siginfo.h new file mode 100644 index 000000000000..d0513880be21 --- /dev/null +++ b/arch/arm/include/uapi/asm/siginfo.h @@ -0,0 +1,13 @@ +#ifndef __ASM_SIGINFO_H +#define __ASM_SIGINFO_H + +#include + +/* + * SIGFPE si_codes + */ +#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + +#endif diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c index da0b33deba6d..911468a3e35a 100644 --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -257,7 +257,7 @@ static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_ if (exceptions == VFP_EXCEPTION_ERROR) { vfp_panic("unhandled bounce", inst); - vfp_raise_sigfpe(0, regs); + vfp_raise_sigfpe(FPE_FIXME, regs); return; }