From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E06182C11E4; Tue, 13 Oct 2026 12:21:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894120; cv=none; b=qGUjcJ2YgU/XDVBl7+Q7i74i+VWa/pIg7bSnTqGNpheWmN7f0FZEC/jeoxRI9ySMrV0pfj7MOziyTtoRNCcOnUEN32xvuOzQdI/D7lj1xww+fAPi4jt0OK35crpUp2SG4jKaYyTwfSTAIQblB0vw7BGLUdh5eM/x4I5ZPQMgvNk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894120; c=relaxed/simple; bh=aMxl5IhBK3fCmHI0Rmfx/7lF/eEUZv1MauEjYTZDMhM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Avg8ayyCDk9e+l15voqsR1GKPzmcD6j4TimCdAaK6bOyMK1J9Q/yS6kXj24Q558jnWt9oijNT/8P6nhRsnvUq8+z9YAvTCB7iZuk5xfiBT7uvEiF3FrW+Vlg+oAPiKMHUn7+5hLPSsmnmrpt8d53KgwULsy1zMVXpGvWq2wUtKc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RiWxjUje; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="RiWxjUje" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 439461F00893; Tue, 13 Oct 2026 12:21:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791894118; bh=HwnvHJpheWE5ZU85yd8sH8RDjwSQnpCvE5bl10tHqis=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RiWxjUjepwIUaYLwvD5oaN8X2BL59xjGJJz5ch/thNsROB8PO6NXPgAypraIYSDA3 zP3/NMfVDp0vIWMjC3QLVi5QM6snwoGEXC3w9196bZsB7jy8S2hdVrWmUbG7ZF0vcd Do79d5YRRwL6g0rF0BbDN+SzJEMTyP6ynqSmPE0Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kees Cook , Jinjie Ruan , Mark Rutland , Yiqi Sun , Will Deacon , Sasha Levin Subject: [PATCH 6.18 454/621] arm64: ptrace: Keep orig_x0 in-sync with x0 on syscall entry Date: Tue, 13 Oct 2026 13:37:29 +0200 Message-ID: <20261013112931.604420053@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112920.855194808@linuxfoundation.org> References: <20261013112920.855194808@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon [ Upstream commit 88b839ce497ccb1ff92f7ae742c78dd2937ba572 ] Commit e057b9477232 ("arm64: syscall: Ensure saved x0 is kept in-sync with tracer updates") attempted to resolve a long-standing issue with syscall entry tracing, where a tracer is able to manipulate the first syscall argument without being subjected to seccomp or audit checking. Unfortunately, that fix was incomplete [1], as it failed to update 'orig_x0' between a tracer updating x0 during a seccomp ptrace exit (SECCOMP_RET_TRACE) and the seccomp filter being re-evaluated. Rather than add hooks to the core seccomp code, instead move the synchronisation code into the ptrace GPR and syscall setting code so that 'orig_x0' is kept up to date with x0 whenever we're stopped on the syscall entry path. Cc: Kees Cook Cc: Jinjie Ruan Cc: Mark Rutland Link: https://sashiko.dev/#/patchset/20260716120640.6590-1-will@kernel.org [1] Reported-by: Yiqi Sun Link: https://lore.kernel.org/all/20260529065444.1336608-1-sunyiqixm@gmail.com/ Fixes: e057b9477232 ("arm64: syscall: Ensure saved x0 is kept in-sync with tracer updates") Fixes: a5cd110cb836 ("arm64/ptrace: run seccomp after ptrace") Tested-by: Jinjie Ruan Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- arch/arm64/kernel/ptrace.c | 50 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index ceb047e7d49f2..8e7f8dedb1cc0 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -560,6 +560,42 @@ static int gpr_get(struct task_struct *target, return membuf_write(&to, uregs, sizeof(*uregs)); } +static void update_syscall_orig_x0_after_ptrace(struct task_struct *target) +{ + struct pt_regs *regs = task_pt_regs(target); + struct kernel_siginfo *info = target->last_siginfo; + + /* + * Skip the update for NO_SYSCALL (set either by the user or the + * tracer), as regs[0] holds the return value (see the comment in + * el0_svc_common()) and can be unwound using syscall_rollback(). + */ + if (regs->syscallno == NO_SYSCALL) + return; + + /* We should only be called when target is in a ptrace stop */ + if (WARN_ON_ONCE(!info)) + return; + + /* + * For compat tasks, orig_r0 is provided directly through GPR index + * 17. + */ + if (is_compat_thread(task_thread_info(target))) + return; + + /* + * Don't update orig_x0 for a syscall-exit-stop, as x0 now contains the + * return value of the system call. + */ + if ((info->si_code & ~0x80) == SIGTRAP && + target->ptrace_message == PTRACE_EVENTMSG_SYSCALL_EXIT) { + return; + } + + regs->orig_x0 = regs->regs[0]; +} + static int gpr_set(struct task_struct *target, const struct user_regset *regset, unsigned int pos, unsigned int count, const void *kbuf, const void __user *ubuf) @@ -575,6 +611,14 @@ static int gpr_set(struct task_struct *target, const struct user_regset *regset, return -EINVAL; task_pt_regs(target)->user_regs = newregs; + + /* + * Keep orig_x0 authoritative so that seccomp (via + * syscall_get_arguments()), audit and the restart path all see the same + * first argument the syscall is dispatched with, even if it has been + * updated by a tracer. + */ + update_syscall_orig_x0_after_ptrace(target); return 0; } @@ -753,6 +797,12 @@ static int system_call_set(struct task_struct *target, return ret; task_pt_regs(target)->syscallno = syscallno; + + /* + * Re-sync orig_x0 in case the syscall number has been changed + * from NO_SYSCALL. + */ + update_syscall_orig_x0_after_ptrace(target); return ret; } -- 2.53.0