From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEB38C433F5 for ; Thu, 3 Feb 2022 19:39:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353803AbiBCTjI (ORCPT ); Thu, 3 Feb 2022 14:39:08 -0500 Received: from mail.efficios.com ([167.114.26.124]:53842 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348659AbiBCTjD (ORCPT ); Thu, 3 Feb 2022 14:39:03 -0500 Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id BB98239236B; Thu, 3 Feb 2022 14:39:02 -0500 (EST) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id kAucsZFzUyfJ; Thu, 3 Feb 2022 14:39:02 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 52703392369; Thu, 3 Feb 2022 14:39:02 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 52703392369 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1643917142; bh=ehEiD5eN73JoYPbHr0aoW8W4nHv8359VE81+kSIwDoo=; h=From:To:Date:Message-Id; b=T4em5BlZ6OZub0BBslsXZbP6uFaUD5tV11pVrMrCp4GCTC6Xu6kXgMUJ3vtaC1g1S SVVyP+HytCNHNI1ODJmEdn+C8Q0JLEzITXv7tjq1dheGPZhvTlUKojQkEAhX/smdR9 SS6Bm9m/d8wxYGqhedQOsNdJMi82/uEQFfqVL9Dtceo0YG0NRJxAxjT6hcNqoaLFNO iDe8JHOj0+QWh9MBfSp/jvFhdBqprm7r2Kl8U6RYBaWJNsS39fAcbHVTp2nyAS56GX AsFAT17U5VELwSWkqaTzoXG0AaC9oPQA7pGbjypEVS3lVpqTBS6BamVCcm3ZjpWLqE 2qPsGM25g+i3A== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 7OvVQPK4blYB; Thu, 3 Feb 2022 14:39:02 -0500 (EST) Received: from localhost.localdomain (192-222-180-24.qc.cable.ebox.net [192.222.180.24]) by mail.efficios.com (Postfix) with ESMTPSA id 118F13922EE; Thu, 3 Feb 2022 14:39:02 -0500 (EST) From: Mathieu Desnoyers To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , "Paul E . McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, Christian Brauner , Florian Weimer , David.Laight@ACULAB.COM, carlos@redhat.com, Peter Oskolkov , libc-coord@lists.openwall.com, Mathieu Desnoyers Subject: [RFC PATCH 2/3] rseq: Introduce extensible rseq ABI Date: Thu, 3 Feb 2022 14:38:52 -0500 Message-Id: <20220203193853.21511-2-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220203193853.21511-1-mathieu.desnoyers@efficios.com> References: <20220203193853.21511-1-mathieu.desnoyers@efficios.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce the extensible rseq ABI, where the feature size supported by the kernel and the required alignment are communicated to user-space through ELF auxiliary vectors. This allows user-space to call rseq registration with a rseq_len of either 32 bytes for the original struct rseq size (which includes padding), or larger. If rseq_len is larger than 32 bytes, then it must be large enough to contain the feature size communicated to user-space through ELF auxiliary vectors. Signed-off-by: Mathieu Desnoyers --- include/linux/sched.h | 4 ++++ kernel/ptrace.c | 2 +- kernel/rseq.c | 33 +++++++++++++++++++++++++++------ 3 files changed, 32 insertions(+), 7 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 508b91d57470..838c9e0b4cae 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1291,6 +1291,7 @@ struct task_struct { #ifdef CONFIG_RSEQ struct rseq __user *rseq; + u32 rseq_len; u32 rseq_sig; /* * RmW on rseq_event_mask must be performed atomically @@ -2260,10 +2261,12 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) { if (clone_flags & CLONE_VM) { t->rseq = NULL; + t->rseq_len = 0; t->rseq_sig = 0; t->rseq_event_mask = 0; } else { t->rseq = current->rseq; + t->rseq_len = current->rseq_len; t->rseq_sig = current->rseq_sig; t->rseq_event_mask = current->rseq_event_mask; } @@ -2272,6 +2275,7 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) static inline void rseq_execve(struct task_struct *t) { t->rseq = NULL; + t->rseq_len = 0; t->rseq_sig = 0; t->rseq_event_mask = 0; } diff --git a/kernel/ptrace.c b/kernel/ptrace.c index eea265082e97..f5edde5b7805 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -800,7 +800,7 @@ static long ptrace_get_rseq_configuration(struct task_struct *task, { struct ptrace_rseq_configuration conf = { .rseq_abi_pointer = (u64)(uintptr_t)task->rseq, - .rseq_abi_size = sizeof(*task->rseq), + .rseq_abi_size = task->rseq_len, .signature = task->rseq_sig, .flags = 0, }; diff --git a/kernel/rseq.c b/kernel/rseq.c index 97ac20b4f738..46dc5c2ce2b7 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -18,6 +18,9 @@ #define CREATE_TRACE_POINTS #include +/* The original rseq structure size (including padding) is 32 bytes. */ +#define ORIG_RSEQ_SIZE 32 + #define RSEQ_CS_PREEMPT_MIGRATE_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE | \ RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT) @@ -86,10 +89,15 @@ static int rseq_update_cpu_id(struct task_struct *t) u32 cpu_id = raw_smp_processor_id(); struct rseq __user *rseq = t->rseq; - if (!user_write_access_begin(rseq, sizeof(*rseq))) + if (!user_write_access_begin(rseq, t->rseq_len)) goto efault; unsafe_put_user(cpu_id, &rseq->cpu_id_start, efault_end); unsafe_put_user(cpu_id, &rseq->cpu_id, efault_end); + /* + * Additional feature fields added after ORIG_RSEQ_SIZE + * need to be conditionally updated only if + * t->rseq_len != ORIG_RSEQ_SIZE. + */ user_write_access_end(); trace_rseq_update(t); return 0; @@ -116,6 +124,11 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t) */ if (put_user(cpu_id, &t->rseq->cpu_id)) return -EFAULT; + /* + * Additional feature fields added after ORIG_RSEQ_SIZE + * need to be conditionally reset only if + * t->rseq_len != ORIG_RSEQ_SIZE. + */ return 0; } @@ -336,7 +349,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, /* Unregister rseq for current thread. */ if (current->rseq != rseq || !current->rseq) return -EINVAL; - if (rseq_len != sizeof(*rseq)) + if (rseq_len != current->rseq_len) return -EINVAL; if (current->rseq_sig != sig) return -EPERM; @@ -345,6 +358,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, return ret; current->rseq = NULL; current->rseq_sig = 0; + current->rseq_len = 0; return 0; } @@ -357,7 +371,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, * the provided address differs from the prior * one. */ - if (current->rseq != rseq || rseq_len != sizeof(*rseq)) + if (current->rseq != rseq || rseq_len != current->rseq_len) return -EINVAL; if (current->rseq_sig != sig) return -EPERM; @@ -366,15 +380,22 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, } /* - * If there was no rseq previously registered, - * ensure the provided rseq is properly aligned and valid. + * If there was no rseq previously registered, ensure the provided rseq + * is properly aligned, as communcated to user-space through the ELF + * auxiliary vector AT_RSEQ_ALIGN. + * + * In order to be valid, rseq_len is either the original rseq size, or + * large enough to contain all supported fields, as communicated to + * user-space through the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE. */ if (!IS_ALIGNED((unsigned long)rseq, __alignof__(*rseq)) || - rseq_len != sizeof(*rseq)) + rseq_len < ORIG_RSEQ_SIZE || + (rseq_len != ORIG_RSEQ_SIZE && rseq_len < offsetof(struct rseq, end))) return -EINVAL; if (!access_ok(rseq, rseq_len)) return -EFAULT; current->rseq = rseq; + current->rseq_len = rseq_len; current->rseq_sig = sig; /* * If rseq was previously inactive, and has just been -- 2.17.1