From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lamorak.hansenpartnership.com (lamorak.hansenpartnership.com [198.37.111.173]) (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 ECC9F3BF2E0; Thu, 15 Jan 2026 18:52:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.37.111.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768503158; cv=none; b=ZgnXlCKZzJ0cAUCrPqQqzy4o9Kh7NsEIHe2RC49hKuWoW1+5AJaOfK05nhbCjZrTAcmKnP63tvypqc+zAAytZvRJQyCOMvLNoEB8Iibfe7GQYMjmqbfku2803A4UYXzZefbSz38Sat5QvecjWLyBGProqjk0/FykGcI57kte4RI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768503158; c=relaxed/simple; bh=iQE8npT3I5smpRHQPeFuhmmIM6w4SGCF+j4B5VJYS9k=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=PnT4nCGiJ2zd8hptH7zalNwe2N6cdurUqeR363FEZvBX4rucHsB6J7R7JgksK+szAJrmYnyqWuAgh2hnt4KCX6Zoj7qz3806QdvPOGXc6df9UAT1QtKQa7kxxxjvjg0j/edaYsZEEyzgtPx2SUkozjndViEHt6+cOgmYrk4p9aw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com; spf=pass smtp.mailfrom=HansenPartnership.com; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b=tfd8+xZd; arc=none smtp.client-ip=198.37.111.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="tfd8+xZd" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1768503154; bh=iQE8npT3I5smpRHQPeFuhmmIM6w4SGCF+j4B5VJYS9k=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=tfd8+xZdnKTSOsefD3qRQ+SU5Z0B0JkHBT9Ohkc+tNSdhGgSUk7QYPkD0LvIyX1rD 70XWXQcStOETY99JbxOxFXr1vVECcWiP7CgtfARHRwNNjj3q0llWJ4sVvgpaLntZ6x F22w9v6NfFvWp6nLCzOMNhjys+oBCUGNzGi4vqug= Received: from lingrow.int.hansenpartnership.com (unknown [IPv6:2601:5c4:4300:d341::a774]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lamorak.hansenpartnership.com (Postfix) with ESMTPSA id 46D581C0231; Thu, 15 Jan 2026 13:52:34 -0500 (EST) Message-ID: <8a25c3aca1abd51f41a6041b84410ca393eca04d.camel@HansenPartnership.com> Subject: Re: [PATCH] scsi: pm8001: Fix data race in sysfs SAS address read From: James Bottomley To: Bart Van Assche , Chengfeng Ye , "Martin K . Petersen" Cc: Jack Wang , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 15 Jan 2026 13:52:33 -0500 In-Reply-To: <2c210e30-e7bd-4b70-ad4e-cc7a1bbb5309@acm.org> References: <20260115171140.281969-1-cyeaa@connect.ust.hk> <2c210e30-e7bd-4b70-ad4e-cc7a1bbb5309@acm.org> Autocrypt: addr=James.Bottomley@HansenPartnership.com; prefer-encrypt=mutual; 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 8mT2Eh9SkH+YVOmaKsajgZgrBxA7fWmGoxXswEVxJIFj3vW7yNc0C5HaUdYa5iGOMs4kg2ht4s7yy7NRQuh7BifWjo6BQ6k4S1H+6axZucxhSV1L6zN9d+lr3Xo/vy1unzA== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2026-01-15 at 09:24 -0800, Bart Van Assche wrote: > On 1/15/26 9:11 AM, Chengfeng Ye wrote: > > diff --git a/drivers/scsi/pm8001/pm8001_ctl.c > > b/drivers/scsi/pm8001/pm8001_ctl.c > > index cbfda8c04e95..e49f11969b3b 100644 > > --- a/drivers/scsi/pm8001/pm8001_ctl.c > > +++ b/drivers/scsi/pm8001/pm8001_ctl.c > > @@ -311,8 +311,15 @@ static ssize_t > > pm8001_ctl_host_sas_address_show(struct device *cdev, > > =C2=A0=C2=A0 struct Scsi_Host *shost =3D class_to_shost(cdev); > > =C2=A0=C2=A0 struct sas_ha_struct *sha =3D SHOST_TO_SAS_HA(shost); > > =C2=A0=C2=A0 struct pm8001_hba_info *pm8001_ha =3D sha->lldd_ha; > > - return sysfs_emit(buf, "0x%016llx\n", > > - be64_to_cpu(*(__be64 *)pm8001_ha- > > >sas_addr)); > > + unsigned long flags; > > + ssize_t ret; > > + > > + spin_lock_irqsave(&pm8001_ha->lock, flags); > > + ret =3D sysfs_emit(buf, "0x%016llx\n", > > + be64_to_cpu(*(__be64 *)pm8001_ha- > > >sas_addr)); > > + spin_unlock_irqrestore(&pm8001_ha->lock, flags); > > + > > + return ret; > > =C2=A0 } > > =C2=A0 static DEVICE_ATTR(host_sas_address, S_IRUGO, > > =C2=A0=C2=A0 =C2=A0=C2=A0 pm8001_ctl_host_sas_address_show, NULL); >=20 > Why isn't READ_ONCE() sufficient? And why explicit > spin_lock_irqsave() and spin_unlock_irqrestore() calls instead of > using scoped_guard()? Do we really care? The host sas address isn't something that changes often, so even if it is being overwritten in an interrupt routine, it's likely with the same value. Whereas taking the internal host lock in a sysfs read routine could potentially be a DoS vector. Regards, James