Return-path: Received: from bues.ch ([80.190.117.144]:49008 "EHLO bues.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751056AbdEaPdA (ORCPT ); Wed, 31 May 2017 11:33:00 -0400 Date: Wed, 31 May 2017 17:32:15 +0200 From: Michael =?UTF-8?B?QsO8c2No?= To: Kalle Valo Cc: Jia-Ju Bai , netdev@vger.kernel.org, linux-wireless@vger.kernel.org, b43-dev@lists.infradead.org, linux-kernel@vger.kernel.org, Larry.Finger@lwfinger.net Subject: Re: [PATCH] b43legacy: Fix a sleep-in-atomic bug in b43legacy_op_bss_info_changed Message-ID: <20170531173107.25eeda48@wiggum> (sfid-20170531_173327_277910_5A17D46F) In-Reply-To: <877f0xnwyk.fsf@kamboji.qca.qualcomm.com> References: <1496225353-5544-1-git-send-email-baijiaju1990@163.com> <877f0xnwyk.fsf@kamboji.qca.qualcomm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/bJgH0wfHcTj06dYHMXr80o9"; protocol="application/pgp-signature" Sender: linux-wireless-owner@vger.kernel.org List-ID: --Sig_/bJgH0wfHcTj06dYHMXr80o9 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 31 May 2017 13:26:43 +0300 Kalle Valo wrote: > Jia-Ju Bai writes: >=20 > > The driver may sleep under a spin lock, and the function call path is: > > b43legacy_op_bss_info_changed (acquire the lock by spin_lock_irqsave) > > b43legacy_synchronize_irq > > synchronize_irq --> may sleep > > > > To fix it, the lock is released before b43legacy_synchronize_irq, and t= he=20 > > lock is acquired again after this function. > > > > Signed-off-by: Jia-Ju Bai > > --- > > drivers/net/wireless/broadcom/b43legacy/main.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/net/wireless/broadcom/b43legacy/main.c b/drivers/n= et/wireless/broadcom/b43legacy/main.c > > index f1e3dad..31ead21 100644 > > --- a/drivers/net/wireless/broadcom/b43legacy/main.c > > +++ b/drivers/net/wireless/broadcom/b43legacy/main.c > > @@ -2859,7 +2859,9 @@ static void b43legacy_op_bss_info_changed(struct = ieee80211_hw *hw, > > b43legacy_write32(dev, B43legacy_MMIO_GEN_IRQ_MASK, 0); > > =20 > > if (changed & BSS_CHANGED_BSSID) { > > + spin_unlock_irqrestore(&wl->irq_lock, flags); > > b43legacy_synchronize_irq(dev); > > + spin_lock_irqsave(&wl->irq_lock, flags); =20 >=20 > To me this looks like a fragile workaround and not a real fix. You can > easily add new race conditions with releasing the lock like this. >=20 I think releasing the lock possibly is fine. It certainly is better than sleeping with a lock held. We disabled the device interrupts just before this line. However I think the synchronize_irq should be outside of the conditional right after the write to B43legacy_MMIO_GEN_IRQ_MASK. (So two lines above) I don't think it makes sense to only synchronize if BSS_CHANGED_BSSID is set. On the other hand b43 does not have this irq-disabling foobar anymore. So somebody must have removed it. Maybe you can find the commit that removed this stuff from b43 and port it to b43legacy? So I would vote for moving the synchronize_irq up outside of the conditional and put the unlock/lock sequence around it. And as a second patch on top of that try to remove this stuff altogether like b43 did. --=20 Michael --Sig_/bJgH0wfHcTj06dYHMXr80o9 Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEihRzkKVZOnT2ipsS9TK+HZCNiw4FAlku4f8ACgkQ9TK+HZCN iw64Kw/+N0S9zSacevNX4mgwvqPGIDwN7o8izrkRy/kxsRiTvbUvi9yZj0ffI/9V pHNNWY/ib1OdV0upbDxW0Rqq5V2OnS5/6hQHNvKKEv+RB70kbpq0sTZi/jLqLedT NM/YqKO/OACjAbT1jx0YlZzeKQkfp5lvd1avL1wwVkFcjSFVAJ/9TnR/4cOWst2R G2zT5SveEAMpOhxlYN/4SA1vpszdW9CzQqBwviVzDA18uRAisrLY+pvIUfRKaj0e GuWpeBC2uFy99ovaaLBk7teEcnRMrqDCgaZOCUsm7ilfkcPxmUPrzBC6aJhGwkRk ge5DyyC98Nn5fY+o6ExUd7a7Cfcug990gjSx1TkJxTGujHP/FSJbZ+glstueQ9Yl BAuUEfI7r/W+J6eid3u+T+bYZrY1E5Mc8DrNOR9u8+pmm8Hjp4nucTdZJ436SYW3 3PpC+WhsyGtlPl7sOHLdv98itsGMB2qU2T2loi9+4LfxCrJrTpzEgt07lusCWje5 01Oh6ilj6kBXL93633/ynLab2rt0zFnvx9Y/2OSRofSxIe9p6b1fcsmmiJNra7WV 3c1ExJphTV0u+UTZpn5fVAYGT8mt6bMjbAdmnbW8iQIsc86BEmIbAf63yUC4rwSU PYggfb7vC69BZjHZsizfo070RqCu5b8t4F/8KtVAVEGv1SBMlb4= =0/6l -----END PGP SIGNATURE----- --Sig_/bJgH0wfHcTj06dYHMXr80o9--