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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A1AD2CED243 for ; Tue, 18 Nov 2025 12:51:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8E35F6B0099; Tue, 18 Nov 2025 07:51:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 894496B00A1; Tue, 18 Nov 2025 07:51:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7D08F6B00A2; Tue, 18 Nov 2025 07:51:58 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 690B96B0099 for ; Tue, 18 Nov 2025 07:51:58 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 0B1D713B151 for ; Tue, 18 Nov 2025 12:51:58 +0000 (UTC) X-FDA: 84123715116.06.6200663 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf15.hostedemail.com (Postfix) with ESMTP id 598CBA0013 for ; Tue, 18 Nov 2025 12:51:55 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=UMShjRt3; spf=none (imf15.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763470316; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=OzxLKs39PWDbcq4Lbqe/ZoP4a39VPMRKYU7TDvRKOxU=; b=GcTOHP63Lbwi7LeTbpfBMV4PjZedsMlhM1bLVcZ+wk/1JS1isDi3efF/uIo40uYOQmFTxQ wZtCI5QcyHj1B+8lPvDv4nsMTFR4VNZMWMFXP0B9y3gqA2zLf4Emy8/VYywD71OphABo6U /VRU8sKpkI9AHh6fsXKFLmFqyY0QW2E= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763470316; a=rsa-sha256; cv=none; b=W0fHjsDl0/+MDaFMAFbluFVcGzH++RdAnGO14Lyo52yCy4PEIal6X3dQ9sFfdOYFMxMrsx vgz3lZoxfWenRlekQZK1eSDbxLlexQDxTCvwcmNz/qIEl+w8BrXfxB00/TD1JveD0qbHSB kE1I7clSSsGBbwZUrQJIpEX6EEGhgbk= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=UMShjRt3; spf=none (imf15.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=OzxLKs39PWDbcq4Lbqe/ZoP4a39VPMRKYU7TDvRKOxU=; b=UMShjRt32ga8qnRRWFrepB2Pgz OgEt5WtRa5Trl4ds6e5rKqrXJoP8wUOyus3IVsusUjlJ8oszfliaxlucomDLrBxZrddCOcny5698t BSk1G9c3nnsYTKVX+xuGppqOi7asRlYQlUXF8Ixxt8JQJ7FDjN3VrqSYyoAt7YTOdzNuCrl9YyMEp oP78RDKeE2AElybsO5Dq48Wmb9I7LQVfi5GyMupPE6LqZ3jCUrzYYPt13Y/p5LtLTlhywjQJK7Ywz 42dI2tc2yvJD+62zjtzY57kSMr9ERElNlra4MidXQcKbuQNE9yng6enKYvdJf2G92TxwnIFoQhMU5 JFgspVcQ==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vLLBW-0000000FUZC-37rp; Tue, 18 Nov 2025 12:51:50 +0000 Date: Tue, 18 Nov 2025 12:51:50 +0000 From: Matthew Wilcox To: Christoph Hellwig Cc: SHAURYA RANE , akpm@linux-foundation.org, shakeel.butt@linux.dev, eddyz87@gmail.com, andrii@kernel.org, ast@kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, skhan@linuxfoundation.org, david.hunter.linux@gmail.com, khalid@kernel.org, syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com Subject: Re: [PATCH] mm/filemap: fix NULL pointer dereference in do_read_cache_folio() Message-ID: References: <20251114193729.251892-1-ssranevjti@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: tmnho5qcjqihp56gyukbdmotrhdh73o6 X-Rspam-User: X-Rspamd-Queue-Id: 598CBA0013 X-Rspamd-Server: rspam01 X-HE-Tag: 1763470315-678894 X-HE-Meta: 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 tJh4z710 my+E7moHQ+1JWZSPFYivfOY28IDxdkq0tb4PZMr+KMAuZ+DfuZlv9mJKfHOf2FRcNSfgnvNUWhjWxeTdMSO7YI+aUKr2XeTphIPTxQR9rHVWMLQCg7uBCyEK/bAgbYD3XzRnUpc6nfJAOca+N5iWhA0XyJAEX1O9b+LYtsdeC4O+1mRagZffwr+2CVQGlp+95tnQCJ7m+VJ4Fy4TJ6TSvE5GZPp+uf5/SXr7mBwZyQoX7cnNnc+C0L9wlGP4Nc0Vo6OyCB92TuP/2L4Nxmt+kmj0CgX80Dw+0d9r8lshjbDWOOd82T7cNc+AJXo+Ji7BQb7sTAu/nlJlDhlPCqtE/LCIBjD/w/PQQJGxr1HgghdQFSLTG6X98PwKF6Ajgwr5g1j/CIm2guFCHwa0Tk4/7DFrncBh0It838QFJS7K7dWdeb7NQSPiF4StbCzFIAQdVyP5GuzXXRxKaPlQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Nov 17, 2025 at 09:05:17PM -0800, Christoph Hellwig wrote: > On Sun, Nov 16, 2025 at 10:32:12PM +0000, Matthew Wilcox wrote: > > I don't think it's necessarily all that hard to make buildid work > > for DAX. It's probably something like: > > > > if (IS_DAX(file_inode(file))) > > kernel_read(file, buf, count, &pos); > > > > but that's just off the top of my head. > > The code should just unconditionally use kernel_read(). Relying > on ->read_folio to just work is only something file system code and > library code called by the file systems can assume. > > Something reading ELF headers has no bunsiness poking into this layer. Please read the rest of the thread; this code can be called in contexts that can't block. That was why I proposed the kiocb_read() refactoring that I would expect you to have an opinion on.