From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-03.galae.net (smtpout-03.galae.net [185.246.85.4]) (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 A1B2D35E930 for ; Mon, 22 Jun 2026 07:32:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.85.4 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782113579; cv=none; b=LNyDPkG+aSzFiRXA1O5ab9u1bTKx0XgD6vE2aY2uqhGWqTclFz5N4HXYSM5Goo1ua4OztBBtJoSWg0ppL78LEATYbuvQGhBYc3y9G+qSiIhpxxAiiMO6eHERn+AHTtcH9OIRBHiUqBI8z8XJJg8E44enwH/bjFxyt8yNLyzeFfU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782113579; c=relaxed/simple; bh=wOS1gYH4Tf4CRu54h7iK37DgFW8FV0uaaTC6GAp3QSM=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=USzZN7ftPPrX9BPcfsOuiGo4EpMPeRrrCLTsORHIcFHBC3RMLVws7zqddHRWPH/Njo1wsop+iE6ZPdiyJpWA8OPcXuw6xRsiSQIkpHhEDNbsoE0q5HnR5r8UBxI8snyWYYFSJ5hizTuR11jGQnnBKHWOxJTGLG7f1JcW1yGUTvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=lK25WbJf; arc=none smtp.client-ip=185.246.85.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="lK25WbJf" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-03.galae.net (Postfix) with ESMTPS id C91EF4E405D6; Mon, 22 Jun 2026 07:32:48 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 9CCB9601BB; Mon, 22 Jun 2026 07:32:48 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 1112F106C898A; Mon, 22 Jun 2026 09:32:43 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1782113568; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=F1WzrJAQoi06uIZ3fIKeNj1JU/5aZLhBz05F4gML+eo=; b=lK25WbJfW41zUnB34avBqSf+9NXYnwgLTQC0ZTcbS9SaYEFGk3hwIgsmPy6qD4mbR1aNJ9 W6dkiQeymFtT31dC06rtuxCRaTzB5DGb7gBhr7c4YaXCLsxvQpO9O/i9Eod1XTv6/XMqZn ZDatIXDlJa7CdO0Rggrp8G7bO1U+WS4q0HbyAozFlcu0u0HJbSmHuaj6QuTY7ExMYzOel0 IKo4bIGoZMiKWaoH946F5VDHMWiQF1gXBjyPyfbQHqE0RaJpup4GJ/WpUUWVATXbbeBLC8 7PvP4E81Osl8ggtteXB6QUOmju2CWUoNOnqPGpDg+DJqUOeDWzfOAmza8zQJ8A== From: Miquel Raynal To: "Luca Ceresoli" Cc: "Dan Carpenter" , "Harshit Mogalapalli" , "Richard Weinberger" , "Vignesh Raghavendra" , "Amit Kumar Mahapatra" , , , Subject: Re: [PATCH] mtd: virt_concat: fix use-after-free in mtd_virt_concat_destroy_joins() In-Reply-To: (Luca Ceresoli's message of "Tue, 16 Jun 2026 22:31:28 +0200") References: <20260614081052.1332702-1-harshit.m.mogalapalli@oracle.com> User-Agent: mu4e 1.12.7; emacs 30.2 Date: Mon, 22 Jun 2026 09:32:43 +0200 Message-ID: <874iiv3u90.fsf@bootlin.com> 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=utf-8 Content-Transfer-Encoding: quoted-printable X-Last-TLS-Session-Version: TLSv1.3 On 16/06/2026 at 22:31:28 +02, "Luca Ceresoli" = wrote: > On Tue Jun 16, 2026 at 12:13 PM CEST, Dan Carpenter wrote: >> On Tue, Jun 16, 2026 at 11:51:53AM +0200, Luca Ceresoli wrote: Yes, container_of() for issue 1 seems to be a better approach. >>> Issue 2: in mtd_virt_concat_destroy_joins(): >>> >>> list_for_each_entry_safe(item, tmp, &concat_node_list, head) { >>> mtd =3D &item->concat->mtd; [0] >>> if (item->concat) { [1] >>> >>> At line [0] we dereference item->concat, but at line [1] we apparently >>> handle the case where item->concat can be NULL. Either [1] is always tr= ue >>> and we can remove the if(), or [1] can be false, so [0] is a bug and sh= ould >>> probably be moved to inside the if(). >> >> That's not a dereference on line 0, it's pointer math. So the code >> works. But a lot of people find the distinction confusing. > > Ah, indeed, you are right on both aspects: it's just pointer math (not a > bug) + it is confusing code. > > So moving [0] inside the if() would be a readability improvement IMO, but > definitely not a bugfix. Yes! Thanks, Miqu=C3=A8l From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4988ECDB46B for ; Mon, 22 Jun 2026 07:33:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:References :In-Reply-To:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rm/JkQOJuf8fH+XNiMDyj5N0gdAY1s7IMvDygJM07jg=; b=mHot/B6xj2QW3k Jawl+ba3uiIohxt3KX91XG/8p+oxiopkydiNrNvT1LbHENqim3IoI76r051SRvcMCOS/08PME1Gpo X1j2UCLWQZAALgUDLZXJm/RTuZ4EbmkyzI7AopBBRBUQtRJUtiq+43ITtTSTg4Z7pJDU55WsqBUk6 UWAe7FPKpRk7x2+TBBU1Ip8eVUPgsWwkpn4kDxFF/DQnz4eRksf/igYOfFaZzki7v+n6inqx6LXp3 nE/WTo1xzEUox5P8CBlS3dx7oKemQBwGV0/ROW5sSdZx3H5VaSDHm9GbPLegnMEN9+vGV86ZinpLK 9gr+YK3LPauo5hljZ+WQ==; 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charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org T24gMTYvMDYvMjAyNiBhdCAyMjozMToyOCArMDIsICJMdWNhIENlcmVzb2xpIiA8bHVjYS5jZXJl c29saUBib290bGluLmNvbT4gd3JvdGU6Cgo+IE9uIFR1ZSBKdW4gMTYsIDIwMjYgYXQgMTI6MTMg UE0gQ0VTVCwgRGFuIENhcnBlbnRlciB3cm90ZToKPj4gT24gVHVlLCBKdW4gMTYsIDIwMjYgYXQg MTE6NTE6NTNBTSArMDIwMCwgTHVjYSBDZXJlc29saSB3cm90ZToKClllcywgY29udGFpbmVyX29m KCkgZm9yIGlzc3VlIDEgc2VlbXMgdG8gYmUgYSBiZXR0ZXIgYXBwcm9hY2guCgo+Pj4gSXNzdWUg MjogaW4gbXRkX3ZpcnRfY29uY2F0X2Rlc3Ryb3lfam9pbnMoKToKPj4+Cj4+PiAJbGlzdF9mb3Jf ZWFjaF9lbnRyeV9zYWZlKGl0ZW0sIHRtcCwgJmNvbmNhdF9ub2RlX2xpc3QsIGhlYWQpIHsKPj4+ IAkJbXRkID0gJml0ZW0tPmNvbmNhdC0+bXRkOyBbMF0KPj4+IAkJaWYgKGl0ZW0tPmNvbmNhdCkg eyBbMV0KPj4+Cj4+PiBBdCBsaW5lIFswXSB3ZSBkZXJlZmVyZW5jZSBpdGVtLT5jb25jYXQsIGJ1 dCBhdCBsaW5lIFsxXSB3ZSBhcHBhcmVudGx5Cj4+PiBoYW5kbGUgdGhlIGNhc2Ugd2hlcmUgaXRl bS0+Y29uY2F0IGNhbiBiZSBOVUxMLiBFaXRoZXIgWzFdIGlzIGFsd2F5cyB0cnVlCj4+PiBhbmQg d2UgY2FuIHJlbW92ZSB0aGUgaWYoKSwgb3IgWzFdIGNhbiBiZSBmYWxzZSwgc28gWzBdIGlzIGEg YnVnIGFuZCBzaG91bGQKPj4+IHByb2JhYmx5IGJlIG1vdmVkIHRvIGluc2lkZSB0aGUgaWYoKS4K Pj4KPj4gVGhhdCdzIG5vdCBhIGRlcmVmZXJlbmNlIG9uIGxpbmUgMCwgaXQncyBwb2ludGVyIG1h dGguICBTbyB0aGUgY29kZQo+PiB3b3Jrcy4gIEJ1dCBhIGxvdCBvZiBwZW9wbGUgZmluZCB0aGUg ZGlzdGluY3Rpb24gY29uZnVzaW5nLgo+Cj4gQWgsIGluZGVlZCwgeW91IGFyZSByaWdodCBvbiBi b3RoIGFzcGVjdHM6IGl0J3MganVzdCBwb2ludGVyIG1hdGggKG5vdCBhCj4gYnVnKSArIGl0IGlz IGNvbmZ1c2luZyBjb2RlLgo+Cj4gU28gbW92aW5nIFswXSBpbnNpZGUgdGhlIGlmKCkgd291bGQg YmUgYSByZWFkYWJpbGl0eSBpbXByb3ZlbWVudCBJTU8sIGJ1dAo+IGRlZmluaXRlbHkgbm90IGEg YnVnZml4LgoKWWVzIQoKVGhhbmtzLApNaXF1w6hsCgpfX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX18KTGludXggTVREIGRpc2N1c3Npb24gbWFpbGlu ZyBsaXN0Cmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vbGludXgt bXRkLwo=