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 9B9DB4ABBD8; Thu, 17 Sep 2026 17:08:38 +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=1789664919; cv=none; b=YTv+1wIphvlEnsNWLLTiK4wHwBc+JKnIB+aRqQxG33iTXhbTbetb2lhBmGo6/caUDlHwrhfhLyuDCN6p7eQQSrwEEJwjnfJtEAxGVaPIEOYXF4JJu290WTnHOWIKQm7Zpg26c9V/LN0xJDqxQUMGom1sxfbwCaT/gQQCURrxRZM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789664919; c=relaxed/simple; bh=3/jtSMZBINfV2DksX548xL8h2/4j0SHNd2ubN1UrOBs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=j2UE4QrxiYC7V9RXGaPg0bEwjxSAjXU3ouYBFGdozDzhkV49xgya/geNCvyVtP9dircg5lXjS6a3CF3Gg0upIdeoa00vNnhe9Qocmg0jGs6T0c1jrkKj0m3DaqRK8PmzzXgGrMvXp2NL+vIry+bL4cPFpbR6GIPWbx75U9qiles= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cK7B0ofZ; 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="cK7B0ofZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0D681F00893; Thu, 17 Sep 2026 17:08:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789664918; bh=2SGKl5B3oud/En7N2p/0pesjgWvoIuMw1iBySQ904Vg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cK7B0ofZUjL0rni2CC9EaWTrAiiJN26RTw4lOQoX7KN0tux8rBwz9J7tmxC9JgeYv hITv7+PZuCe47RUFhb9GwLRA2rixScJYIYMdgDME2doZHFf3H4GNBLTdF5UvMW+USd Jo2jhS+GjlnS9tSsBpppr7iL2DZeH2GecKVcPmfc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Pu Hu , Hongyan Xia , "Masami Hiramatsu (Google)" , Will Deacon , Sasha Levin Subject: [PATCH 6.18 0532/1250] arm64: kprobes: Allow reentering kprobes while single-stepping Date: Thu, 17 Sep 2026 16:05:27 +0100 Message-ID: <20260917151606.360628164@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151551.901433442@linuxfoundation.org> References: <20260917151551.901433442@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: Pu Hu [ Upstream commit 23f851ac0078a908bf3422d6467ebc1db5828c46 ] A kprobe can be hit while another kprobe is in KPROBE_HIT_SS state. This can happen when tracing or perf code runs from the debug exception path while the first kprobe is preparing or executing its out-of-line single-step instruction. Currently arm64 treats a kprobe hit in KPROBE_HIT_SS as unrecoverable, the same as a hit in KPROBE_REENTER. This is too strict. A hit in KPROBE_HIT_SS is still a one-level reentry and can be handled by saving the current kprobe state and setting up single-step for the new probe, just like reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE. The truly unrecoverable case is hitting another kprobe while already in KPROBE_REENTER, because the reentry save area has already been consumed. Move KPROBE_HIT_SS to the recoverable reentry cases and leave KPROBE_REENTER as the unrecoverable nested reentry case. This change also requires saving saved_irqflag in struct prev_kprobe. When a nested kprobe calls kprobes_save_local_irqflag(), it overwrites kcb->saved_irqflag with the currently masked DAIF value, losing the outer kprobe's original DAIF state. Without this fix, when the outer kprobe's single-step finishes, kprobes_restore_local_irqflag() applies the wrong DAIF mask and leaves interrupts permanently disabled. Extend struct prev_kprobe with a saved_irqflag field and save/restore it alongside kp and status. This ensures the outer kprobe's original interrupt state is preserved across reentry. This mirrors the x86 fix in commit 6a5022a56ac3 ("kprobes/x86: Allow to handle reentered kprobe on single-stepping"). Signed-off-by: Pu Hu Signed-off-by: Hongyan Xia Reviewed-by: Masami Hiramatsu (Google) Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- arch/arm64/include/asm/kprobes.h | 6 ++++++ arch/arm64/kernel/probes/kprobes.c | 23 ++++++++++++++++++++++- 2 files changed, 28 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h index f2782560647be..35ce2c94040ef 100644 --- a/arch/arm64/include/asm/kprobes.h +++ b/arch/arm64/include/asm/kprobes.h @@ -26,6 +26,12 @@ struct prev_kprobe { struct kprobe *kp; unsigned int status; + + /* + * The original DAIF state of the outer kprobe, saved here before + * a nested kprobe overwrites kcb->saved_irqflag during reentry. + */ + unsigned long saved_irqflag; }; /* per-cpu kprobe control block */ diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index 43a0361a8bf04..7133da1653964 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -174,12 +174,27 @@ static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) { kcb->prev_kprobe.kp = kprobe_running(); kcb->prev_kprobe.status = kcb->kprobe_status; + + /* + * Save the outer kprobe's original DAIF flags before the nested + * kprobe calls kprobes_save_local_irqflag() and overwrites + * kcb->saved_irqflag. Without this, the outer kprobe will restore + * the wrong DAIF state and leave interrupts permanently masked. + */ + kcb->prev_kprobe.saved_irqflag = kcb->saved_irqflag; } static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) { __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); kcb->kprobe_status = kcb->prev_kprobe.status; + + /* + * Restore the outer kprobe's saved_irqflag so that when its + * single-step completes, kprobes_restore_local_irqflag() uses + * the correct original DAIF value. + */ + kcb->saved_irqflag = kcb->prev_kprobe.saved_irqflag; } static void __kprobes set_current_kprobe(struct kprobe *p) @@ -240,10 +255,16 @@ static int __kprobes reenter_kprobe(struct kprobe *p, switch (kcb->kprobe_status) { case KPROBE_HIT_SSDONE: case KPROBE_HIT_ACTIVE: + case KPROBE_HIT_SS: + /* + * A probe can be hit while another kprobe is preparing or + * executing its XOL single-step instruction. This is still a + * recoverable one-level reentry, so handle it in the same way as + * reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE. + */ kprobes_inc_nmissed_count(p); setup_singlestep(p, regs, kcb, 1); break; - case KPROBE_HIT_SS: case KPROBE_REENTER: pr_warn("Failed to recover from reentered kprobes.\n"); dump_kprobe(p); -- 2.53.0