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 8392F214813; Thu, 6 Aug 2026 00:02:41 +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=1785974566; cv=none; b=NTuiKyqACYnGCGWDS5mgIxXj43V6rbRcB3XbOcVc4/sadY4Mu6IKLc0u0tqzTK1wPI8xgU3tym8uOnRg/2rDyuzqy9+S/PziQmaa1AU3m+LKN+k8wVfAhHMnyIssjJ8W+ChguWY5BygHpMqRy3euxyWg7WC2gtwkkfX8VFi1KF4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785974566; c=relaxed/simple; bh=maLTdq9S0pOK5FWskgeV2YIL0eIKlKHfejHoTiyeeVs=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=Lguy/4ldB747uSAWVuJMhOu2aQLInX8FD7xKDGJweZ2S+LWKbgU6MvlFnpMKzPB+uVV3Eqm22v62ZtfXRe8sH8/xq1T7BfTnEi3TkLj0dJQdXm1MLMBQBk3LtfNSemxIUNPhLqF6v+s4dPpYQjC1k1QN67+cfRLuXM8c98nhZY8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LvRADHmf; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="LvRADHmf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B8E61F000E9; Thu, 6 Aug 2026 00:02:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785974560; bh=v14uNn/Psbc3r2oCTQLvFgoA/nZ54LrAncPHpTkAZ+s=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=LvRADHmf5ITE06u5UT+i1rpzjfzWQ1dlrtuwoFDrJv8byyl2nt1wCtMNc9KjKu5hM nlPW33FinuMg83VjKH20uFsjw6mr8lVCHdd9wGWM02GdI72QbIJdmE8t/nwCU7g096 938cM0ywaQNqHrhIvjb32h5sWt8oOZeUk3qP+xcFhwakvjMZ/UYyE5DBpKUvSdg77o 9bOiLio2ajBJhKKlAl+nSZs/AfUrwgjvHhN8mBzwd3r2+FcZQPOKXormECfTikZp0v WEw6s2SwTjyhmYIXfVIID9V2KEMxJd+dmofvwaVrRZwGbYDyPXiVyxDYSEVOys98QN udjp6OB/nMwDA== Date: Thu, 6 Aug 2026 09:02:35 +0900 From: Masami Hiramatsu (Google) To: Luigi Rizzo Cc: Naveen N Rao , Luigi Rizzo , "David S . Miller" , JP Kobryn , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kprobes: Fix NULL pointer dereference in unregister_kretprobes() Message-Id: <20260806090235.e40c75f84f8a01b9a80fd570@kernel.org> In-Reply-To: <20260805161221.2428623-1-lrizzo@google.com> References: <20260805161221.2428623-1-lrizzo@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 5 Aug 2026 16:12:21 +0000 Luigi Rizzo wrote: > In unregister_kretprobes(), rps[i]->rph can be NULL e.g. when called > after kretprobe failed registration. Under !CONFIG_KRETPROBE_ON_RETHOOK, > the unconditional access to rps[i]->rph->rp, causes a kernel panic due > to NULL pointer dereference. This is not a bug, since if register_kretprobe(rp) fails, rp must NOT be passed to unregister_kretprobe(rp). Or, do you find any cases where register_kretprobe() fails, preventing proper cleanup, and requiring unregister_kretprobe()? If so, we have to fix that case. > > Add a NULL check for rps[i]->rph before invoking rcu_assign_pointer(). > But this could be a kind of protective improvemet for someone misunderstand that. Thank you, > Fixes: d839a656d0f3 ("kprobes: consistent rcu api usage for kretprobe holder") > Signed-off-by: Luigi Rizzo > --- > kernel/kprobes.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index bfc89083daa93..5dd4786c455de 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -2359,7 +2359,8 @@ void unregister_kretprobes(struct kretprobe **rps, int num) > #ifdef CONFIG_KRETPROBE_ON_RETHOOK > rethook_free(rps[i]->rh); > #else > - rcu_assign_pointer(rps[i]->rph->rp, NULL); > + if (rps[i]->rph) > + rcu_assign_pointer(rps[i]->rph->rp, NULL); > #endif > } > > -- > 2.48.1.500.g5897711438-goog > > -- Masami Hiramatsu (Google)