From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f171.google.com (mail-pl1-f171.google.com [209.85.214.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C4302D61B for ; Thu, 20 Jun 2024 19:48:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718912886; cv=none; b=pl6h2O5y1EShyWKKazA2NpilXfVqYA7YIYzxe8Bytfd0PuWZazZEtSHzwsq/IS2tboNODFQ4TaYxKoXAZsZplZB4xWuuon/gpdfhKg6Bu1WPzdIAjSe0Iwp2SHSXN64exTaDUE67fDKYBVECkhCFrQMEoN1Xpn+TROFZ0kQ3pNQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718912886; c=relaxed/simple; bh=awUqwE93wXcTKvo7ol88UKTqegDT1C9qpGNi09weIsE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KZK5nezGHOM2C5AcXw6LLhpb2Co0KPZuIM+7wznpeIN2Azyq8QNSBT8uReCQS8qZ7smt2CofR1BNsCMe1ruRrSi34CGj+IKVCtgzgb3XoZ01mc6vAzzVQygPOs+fj1Id8n1juJIG/4XRK5k42L4CrF/KwFSvkgrxNByvOe0YwZk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=ceUta9yT; arc=none smtp.client-ip=209.85.214.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="ceUta9yT" Received: by mail-pl1-f171.google.com with SMTP id d9443c01a7336-1f6b0a40721so9712175ad.2 for ; Thu, 20 Jun 2024 12:48:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1718912884; x=1719517684; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=z3gaAAA9tFzbTfrmb6ppBykngzDxoq0Px2MEPQ4ymLY=; b=ceUta9yTbf9Mqsk+Eiz+3nzwUsvOYtrT5LSwDmxVIVCUj52gRtg0h5AKXV4Za6iUwa PbCxrjbyh2PIGBbIwv2MrAvhpvuROkcCatw/yuw96tijQg6VQo8nU9eZmbJNcij81DKN aGfgcSl8IRhW/oCfzBHEy0kqdS6uaQXTv3bZo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718912884; x=1719517684; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=z3gaAAA9tFzbTfrmb6ppBykngzDxoq0Px2MEPQ4ymLY=; b=qyaoriCi4ypEtR/ErbjhAwa75Xa9vyr8b1Zp9TI2rU+dJletWxf9DR3Z0iZX9SSuJw tkEADFKaDfqCH+WMb2a+xvqroCvS9qCjWIVS/nrjs7CWSOfOFiv42TKKa0U43dhYFqpa jBJVs6rCC3RyBMSgFUrF/Lmq2s7gz3fby7QjfHds3UwZau9zb/4AE61pLpCycjB6eY8T +CpFgGsutdLlm+H0K5422VrJZfVQD243cqYXTqLfNubzOfdrxoDlYzG++pj4ZwB5TaBb uDjOEPvO4Ya3CbxTNmQRmhk/frYjxVfrTRr7qrzakHp492m+RzIpsmAeaT21ZJ1+BwZw t0Sg== X-Forwarded-Encrypted: i=1; AJvYcCUhi0i0K5C3BxofUpqkMaPf1zDMlvdC5XQ8UzdFJU7LnkhCCzZGYJxAZYfEUhNbVYlJpV4DTK8h2nErO4zwsTJyAaxA4g+R1kaep7ur X-Gm-Message-State: AOJu0YzUoL3Mk0A6H0QhBYblDSRjwnZjiBe8nT2uLIPtv/BPqysUMR/Y dFk7otB5GJ6NOI6g/h4I3z/LB9JVlYrr5H3rfk+fmZ9EfxrWY1wqGxiiEwIWsg== X-Google-Smtp-Source: AGHT+IEwL8sWyeO+AO4RDSEBECQdktpgu8GHQ417gFO1L6pv/TF+6VFPQWQRBNh6mAnIj3O6xdidjg== X-Received: by 2002:a17:902:ee86:b0:1f7:2051:c816 with SMTP id d9443c01a7336-1f9aa40521dmr60222285ad.35.1718912883581; Thu, 20 Jun 2024 12:48:03 -0700 (PDT) Received: from localhost ([2620:15c:9d:2:3c9c:a224:3ec6:17d2]) by smtp.gmail.com with UTF8SMTPSA id d9443c01a7336-1f9eb323636sm10805ad.102.2024.06.20.12.48.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Jun 2024 12:48:03 -0700 (PDT) Date: Thu, 20 Jun 2024 12:48:01 -0700 From: Brian Norris To: Kalle Valo Cc: Sascha Hauer , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, David Lin , Francesco Dolcini Subject: Re: [PATCH] [RFC] mwifiex: Fix NULL pointer deref Message-ID: References: <20240619070824.537856-1-s.hauer@pengutronix.de> <87wmmll5mf.fsf@kernel.org> 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-Disposition: inline In-Reply-To: <87wmmll5mf.fsf@kernel.org> Hi Sascha, On Wed, Jun 19, 2024 at 11:05:28AM +0300, Kalle Valo wrote: > Sascha Hauer writes: > > > When an Access Point is repeatedly started it happens that the > > interrupts handler is called with priv->wdev.wiphy being NULL, but > > dereferenced in mwifiex_parse_single_response_buf() resulting in: > > > > | Unable to handle kernel NULL pointer dereference at virtual address 0000000000000140 ... > > | pc : mwifiex_get_cfp+0xd8/0x15c [mwifiex] > > | lr : mwifiex_get_cfp+0x34/0x15c [mwifiex] > > | sp : ffff8000818b3a70 > > | x29: ffff8000818b3a70 x28: ffff000006bfd8a5 x27: 0000000000000004 > > | x26: 000000000000002c x25: 0000000000001511 x24: 0000000002e86bc9 > > | x23: ffff000006bfd996 x22: 0000000000000004 x21: ffff000007bec000 > > | x20: 000000000000002c x19: 0000000000000000 x18: 0000000000000000 > > | x17: 000000040044ffff x16: 00500072b5503510 x15: ccc283740681e517 > > | x14: 0201000101006d15 x13: 0000000002e8ff43 x12: 002c01000000ffb1 > > | x11: 0100000000000000 x10: 02e8ff43002c0100 x9 : 0000ffb100100157 > > | x8 : ffff000003d20000 x7 : 00000000000002f1 x6 : 00000000ffffe124 > > | x5 : 0000000000000001 x4 : 0000000000000003 x3 : 0000000000000000 > > | x2 : 0000000000000000 x1 : 0001000000011001 x0 : 0000000000000000 > > | Call trace: > > | mwifiex_get_cfp+0xd8/0x15c [mwifiex] > > | mwifiex_parse_single_response_buf+0x1d0/0x504 [mwifiex] > > | mwifiex_handle_event_ext_scan_report+0x19c/0x2f8 [mwifiex] > > | mwifiex_process_sta_event+0x298/0xf0c [mwifiex] > > | mwifiex_process_event+0x110/0x238 [mwifiex] > > | mwifiex_main_process+0x428/0xa44 [mwifiex] > > | mwifiex_sdio_interrupt+0x64/0x12c [mwifiex_sdio] > > | process_sdio_pending_irqs+0x64/0x1b8 > > | sdio_irq_work+0x4c/0x7c > > | process_one_work+0x148/0x2a0 > > | worker_thread+0x2fc/0x40c > > | kthread+0x110/0x114 > > | ret_from_fork+0x10/0x20 > > | Code: a94153f3 a8c37bfd d50323bf d65f03c0 (f940a000) > > | ---[ end trace 0000000000000000 ]--- > > > > Fix this by adding a NULL check before dereferencing this pointer. > > > > Signed-off-by: Sascha Hauer > > > > --- > > > > This is the most obvious fix for this problem, but I am not sure if we > > might want to catch priv->wdev.wiphy being NULL earlier in the call > > chain. > > I haven't looked at the call but the symptoms sound like that either we > are enabling the interrupts too early or there's some kind of locking > problem so that an other cpu doesn't see the change. I agree with Kalle that there's a different underlying bug involved, and (my conclusion:) we shouldn't whack-a-mole the NULL pointer without addressing the underlying problem. Looking a bit closer (and without much other context to go on): I believe that one potential underlying problem is the complete lack of locking between cfg80211 entry points (such as mwifiex_add_virtual_intf() or mwifiex_cfg80211_change_virtual_intf()) and most stuff in the main loop (mwifiex_main_process()). The former call sites only hold the wiphy lock, and the latter tends to ... mostly not hold any locks, but rely on sequentialization with itself, and using its |main_proc_lock| for setup and teardown. It's all really bad and ready to fall down like a house of cards at any moment. Unfortunately, no one has spent time on rearchitecting this driver. So it's possible that mwifiex_process_event() (mwifiex_get_priv_by_id() / mwifiex_get_priv()) is getting a hold of a not-fully-initialized 'priv' structure. BTW, in case I can reproduce and poke at your scenario, what exactly is your test case? Are you just starting / killing / restarting hostapd in a loop? Are you running a full network manager stack that's doing something more complex (e.g., initiating scans)? Can you reproduce with some more targeted set of `iw` commands? (`iw phy ... interface add ...; iw dev ... del`) Is there anything else interesting in the dmesg logs? (Some of the worst behaviors in this driver come when we see command timeouts and mwifiex_reinit_sw(), for example.) Or barring that, can you get some kind of trace of the nl80211 command sequence, so it's clearer which command(s) are involved leading up to the problem? Brian