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 ED2C917993; Thu, 25 Jun 2026 04:38:39 +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=1782362320; cv=none; b=d54okcjnDM7jvHRRzJ24GDYurqcEP8hAflT5Y5fjH80BAJP0WAR56cTQLa5e17nKcNtikjdwIgDLJDEolwg0P7qQmLHqFERoVf6NhZYGANxFEcJHAOnoKbsorfLLjL0CFIL62b1t3N2vqNjTStPlWYt18bY1SP8FCavm1suolqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782362320; c=relaxed/simple; bh=Ghg+es7PMWHvyIWYOB4GuTY+eeE98RJnbilsdWX5+iE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=QjYPe4xoHfNM1kyvphVg6NqPsjc4UglAEDUoE8WuglsCDw+2k5Wr3aIEKhcMatbKPSiPkZ+gKB5iri9kQEvlcblXKQOCyS3TXME05qj6RHQsszXru3tIuITLdBgSMSjOhS6cWbze6fB3XP+AnT3oGjUO71vW/Xv3myeR+DjIlz4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iUJ6ak8K; 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="iUJ6ak8K" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C8891F000E9; Thu, 25 Jun 2026 04:38:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782362319; bh=en/Q8rhQAhmFAKqfB0zVLLdT4CQGk9nawe4wXWP9Uuk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=iUJ6ak8K6MVKcWs+XJD/5EipmDKpowL/HRiXNnhTNRTP+ywSq97hI5SCgLaUmAG0q 3pHOL65slEh8utRnOqcHdwjgckD1jwYKbvDtk/mSXuGUwVqNHknJKkl1k1X/gf93Mr p2nS8Hhrn1/0r/7mdP11exYhfua6NwN828eOrlz7aJB5QTLFVNtRTiyPQGFBg/lW1i pLeuKGK0z/J8BXZzlwWjs/EM++hBZuz3U/k2d9ziGES/vXSzhyfGGyOaWFZJWS883r HYeSYvXMH1yLI8oPdk25XPgZNVmVSdccWzFEpoVsFp+Kcs0aH5YghsukLrZDKRkcIs E1Dq0Uv2Zagbg== Message-ID: <80f44ace-9231-4b4e-9e47-cbe49b3e2d3e@kernel.org> Date: Thu, 25 Jun 2026 06:38:35 +0200 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] serial: 8250: fix use-after-free in IRQ chain handling To: Jing Wu Cc: gregkh@linuxfoundation.org, avorontsov@ru.mvista.com, alan@redhat.com, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, wangzhaolong@fnnas.com References: <20260624-bug-221579-8250-shared-irq-race-v5-1-15d841f89e1e@gmail.com> <20260624084352.2978059-1-realwujing@gmail.com> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 24. 06. 26, 10:43, Jing Wu wrote: > From: Qiliang Yuan > > On Wed, Jun 24, 2026 at 05:31:59AM +0200, Jiri Slaby wrote: >> So what is the reason to switch from guards to manual locking? > > Scope-based guards release the lock at the end of the enclosing block, > but the fix requires hash_mutex to be held across request_irq() and > released at different exit points: > > 1. IS_ERR(i) -- release hash_mutex and return error. > 2. Already in chain -- release i->lock, release hash_mutex, return 0. > 3. First port, request_irq() fails -- cleanup under hash_mutex, then > release it and return error. > 4. First port, request_irq() succeeds -- release hash_mutex, return 0. > > These paths span different nesting levels and early returns, so scope > guards cannot express the required lock lifecycle. The same applies to > i->lock: it must be dropped before calling request_irq() (cannot hold a > spinlock while sleeping), but hash_mutex must remain held across the > call, which also breaks the guard model. I don't follow, the function now looks like this: mutex_lock(&hash_mutex); i = serial_get_or_create_irq_info(up); if (IS_ERR(i)) { mutex_unlock(&hash_mutex); return PTR_ERR(i); } /* ... */ spin_lock_irq(&i->lock); if (i->head) { list_add(&up->list, i->head); spin_unlock_irq(&i->lock); mutex_unlock(&hash_mutex); return 0; } INIT_LIST_HEAD(&up->list); i->head = &up->list; spin_unlock_irq(&i->lock); ret = request_irq(up->port.irq, serial8250_interrupt, up->port.irqflags, up->port.name, i); if (ret < 0) { serial_do_unlink(i, up); mutex_unlock(&hash_mutex); return ret; } mutex_unlock(&hash_mutex); return 0; What am I missing? thanks, -- js suse labs