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 DD8ED24678D; Thu, 6 Nov 2025 16:06:31 +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=1762445194; cv=none; b=crdu9dMjiOqfVjd57T77ggw3+CKPlsLmjN6oFxrjs5ZfBtgUnOnO3G/pcHCzn+uHCQB5KxR8BZuj2WmMj14qZ8X7/3xoKVFoClRReEYBWx5MYDITPKlsgxmrYFbIM70wOckqwxfaH5+DUdXiNmuoYaWW2WqngNnRNd1l1HzHAt0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762445194; c=relaxed/simple; bh=mXJ4vp+epi5Fb1WEW5ijZ7ofXEGQBLcvFtAk8QvOEQw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=M96+G/k/cZZ+o6BvZu1d+G8vLVSPxoDvkZYlQA+OOirqqQWkL8XMR6RZmHB9JUMR6IP2WKqH4By6omx++8fHU/QmOKloycQbLB51NYswdj48BOccUJc4KH+kj06RWe5xEhy22rGDAQ1HFtI5DbF+u67t6CM2pCuKTsH56Xa5KB4= 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=V6tGnQ/t; 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="V6tGnQ/t" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1762445190; bh=mXJ4vp+epi5Fb1WEW5ijZ7ofXEGQBLcvFtAk8QvOEQw=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=V6tGnQ/tZlpuTRERYV2IVq1RfVkCSqG6CcbF+1BKwBam3SxmYl57oJTk4KvnAxPIm 7HnHmPPhY0UiV8eTz/9zeK3xduufOgwy+NuCTgukGxRj2Czhb1lSdc/mFM9dhnzKyc ZNQAfpni9HjODCAOMdNOrQFjnCDo0FiIrcP8qTsM= Received: from lingrow.int.hansenpartnership.com (unknown [IPv6:2601:5c4:4302:c21::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 8198D1C01CB; Thu, 06 Nov 2025 11:06:30 -0500 (EST) Message-ID: Subject: Re: [PATCH] scsi: fix uninitialized pointers with free attr From: James Bottomley To: Dan Carpenter Cc: Ally Heev , "Martin K. Petersen" , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 06 Nov 2025 11:06:29 -0500 In-Reply-To: References: <20251105-aheev-uninitialized-free-attr-scsi-v1-1-d28435a0a7ea@gmail.com> <6d199d062b16abfbf083750820d7a39cb2ebf144.camel@HansenPartnership.com> <407aed0ff7be4fdcafebd09e58e25496b6b4fec0.camel@HansenPartnership.com> 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-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2025-11-06 at 17:46 +0300, Dan Carpenter wrote: > On Wed, Nov 05, 2025 at 10:32:19AM -0500, James Bottomley wrote: > > > > > diff --git a/drivers/scsi/scsi_debug.c > > > > > b/drivers/scsi/scsi_debug.c > > > > > index > > > > > b2ab97be5db3d43d5a5647968623b8db72448379..89b36d65926bdd15c0a > > > > > e93a > > > > > 6bd2 > > > > > ea968e25c0e74 100644 > > > > > --- a/drivers/scsi/scsi_debug.c > > > > > +++ b/drivers/scsi/scsi_debug.c > > > > > @@ -2961,11 +2961,11 @@ static int resp_mode_sense(struct > > > > > scsi_cmnd > > > > > *scp, > > > > > =C2=A0 int target_dev_id; > > > > > =C2=A0 int target =3D scp->device->id; > > > > > =C2=A0 unsigned char *ap; > > > > > - unsigned char *arr __free(kfree); > > > > > =C2=A0 unsigned char *cmd =3D scp->cmnd; > > > > > =C2=A0 bool dbd, llbaa, msense_6, is_disk, is_zbc, is_tape; > > > > > =C2=A0 > > > > > - arr =3D kzalloc(SDEBUG_MAX_MSENSE_SZ, GFP_ATOMIC); > > > > > + unsigned char *arr __free(kfree) =3D > > > > > kzalloc(SDEBUG_MAX_MSENSE_SZ, GFP_ATOMIC); > > > > > + > > > >=20 > > > > Moving variable assignments inside code makes it way harder to > > > > read. Given that compilers will eventually detect if we do a > > > > return before initialization, can't you have smatch do the same > > > > rather than trying to force something like this? > > >=20 > > > This isn't a Smatch thing, it's a change to checkpatch. > > >=20 > > > (Smatch does work as you describe). > >=20 > > So why are we bothering with something like this in checkpatch if > > we can detect the true problem condition and we expect compilers to > > catch up?=C2=A0 Encouraging people to write code like the above isn't i= n > > anyone's best interest. >=20 > Initializing __free variables has been considered best practice for a > long time.=C2=A0 Reviewers often will complain even if it doesn't cause a > bug. Well, not responsible for the daft ideas other people have. However, why would we treat a __free variable any differently from one without the annotation? The only difference is that a function gets called on it before exit, but as long as something can detect calling this on uninitialized variables their properties are definitely no different from non-__free variables so the can be treated exactly the same. To revisit why we do this for non-__free variables: most people (although there are definitely languages where this isn't true and people who think we should follow this) think that having variables at the top of a function (or at least top of a code block) make the code easier to understand. Additionally, keeping the variable uninitialized allows the compiler to detect any use before set scenarios, which can be somewhat helpful detecting code faults (I'm less persuaded by this, particularly given the number of false positive warnings we've seen that force us to add annotations, although this seems to be getting better). So either we throw out the above for everything ... which I really wouldn't want, or we enforce it for *all* variables. Regards, James