From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A3B1B44AB89; Fri, 28 Aug 2026 12:09:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787918965; cv=none; b=SSzmitNod4Za4y07/1z+fH8mVEj3Hj/Cp6fwKxoSTku5LJdAoJEgKUeIWEn2egslSDN02pD+XCL/AEK5c0jw/zDnfPyp3I/qBTNFb24k0N8+Gdwc/ZegXbah0qnqlAtEjnamylAHj/CQwAASXItmEloafLOFcKdw7Pdz0OIQmZ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787918965; c=relaxed/simple; bh=MljRQWlGTL3dzK1MXg4OIWw8gQgURX7U+bXzXlpvLmQ=; h=Date:From:To:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ke4xxR8/xsg44h1ULw4embdO/CGBZ2cV1CFf8OnocA/Phv2pMN7VF7fp3wR0cfwgj+SC+lp1pzCjpKzvUGMFNDVKH6TDJg0+gI+CBcV8rZHXN9f+pDlS+ry+NqMs6NJElWARvgf4PY/G0CsLsP+D7ScaynSXhj5VX4QqQXvQRAo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ziZNJ6e4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ziZNJ6e4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED4821F000E9; Fri, 28 Aug 2026 12:09:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787918952; bh=48rzmK+HCqiY8vexqGfrnERuQwA101HhhU1exDdQKNY=; h=Date:From:To:Subject:References:In-Reply-To; b=ziZNJ6e4ibLphgse0OciC/Kx3bJvOJbYdKy1Jq2MHs+TGq8RmIwZrbCz+zcYrZyB4 XfuCL81+SgV370V23RwBXGaVlHU9byHsdWhSkMmQMlawMhVDBVxPiCeGfhAiu0yGp2 fE5VSh19EZh3D20kwzfllQD+Lx57N66TIdS04B1o= Date: Fri, 28 Aug 2026 14:07:30 +0200 From: Greg KH To: Gao Xiang , cve@kernel.org, linux-kernel@vger.kernel.org, linux-cve-announce@vger.kernel.org Subject: Re: CVE-2026-80697: erofs: ensure valid f_path for page cache sharing Message-ID: <2026082838-penalty-stark-190f@gregkh> References: <2026082805-CVE-2026-80697-4e8a@gregkh> <2026082849-janitor-stonework-71c9@gregkh> 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=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Aug 28, 2026 at 07:29:59PM +0800, Gao Xiang wrote: > On Fri, Aug 28, 2026 at 12:59:00PM +0200, Greg KH wrote: > > On Fri, Aug 28, 2026 at 03:49:05PM +0800, Gao Xiang wrote: > > > Hi Greg, > > > > > > On Fri, Aug 28, 2026 at 08:53:20AM +0200, Greg Kroah-Hartman wrote: > > > > From: Greg Kroah-Hartman > > > > > > > > Description > > > > =========== > > > > > > > > In the Linux kernel, the following vulnerability has been resolved: > > > > > > > > erofs: ensure valid f_path for page cache sharing > > > > > > > > Previously, backing files for page cache sharing were set up with > > > > f_path left as NULL (only f_inode was valid). It worked, but a recent > > > > mincore fix relies on f_path.mnt and crashes (found by "erofs/028" on > > > > 7.2-rc4): > > > > > > > > BUG: kernel NULL pointer dereference, address: 0000000000000018 > > > > #PF: supervisor read access in kernel mode > > > > #PF: error_code(0x0000) - not-present page > > > > PGD 0 P4D 0 > > > > Oops: Oops: 0000 [#1] SMP PTI > > > > CPU: 3 UID: 0 PID: 675528 Comm: fincore Not tainted 7.2.0-rc4-00002-g[]-dirty #1 PREEMPT(lazy) > > > > Hardware name: Red Hat KVM, BIOS 1.16.0-4.al8 04/01/2014 > > > > RIP: 0010:__do_sys_mincore+0xc0/0x2c0 > > > > ... > > > > > > > > Specify valid paths using valid disconnected dentries together with > > > > erofs_ishare_mnt instead of leaving f_path empty, so they are more > > > > like real backing files in a pseudo filesystem and standard > > > > backing_file_open() can be used directly. > > > > > > > > The Linux kernel CVE team has assigned CVE-2026-80697 to this issue. > > > > > > > > > > > > Affected and fixed versions > > > > =========================== > > > > > > > > Issue introduced in 7.1.4 with commit 04ba248d02d9eaa3d9077b00a6134caa75fa3e90 and fixed in 7.1.8 with commit 3879657c4ffd81b9a42cf575fc6cb60201032587 > > > > Issue introduced in 5.15.217 with commit 7368bec565bac3e536cd43579dbde1e715e6ba61 > > > > Issue introduced in 6.1.184 with commit b2f3d94ea310bea9d36d53e9d9b3f45e86c1d893 > > > > Issue introduced in 6.6.145 with commit 744b23aa430d52f5c8e4dbff7d71496d6643bed2 > > > > Issue introduced in 6.12.96 with commit 8344bdf0629457e532797b42d9d2bbf2a2900bbf > > > > Issue introduced in 6.18.39 with commit 5c942ad7df75925ee166e7f0fb36892d8dde376b > > > > > > I don't think that is correct, although commit e187bc02f8fa > > > ("mm: do file ownership checks with the proper mount idmap") directly > > > causes this issue, the entire page cache sharing feature was introduced > > > in Linux 7.0. > > > > Yes, but it was backported to all of the above stable kernels as well, > > which is why they are listed that way. > > I know e187bc02f8fa was backported to these kernels, but as I said, > this commit directly caused the issue (without e187bc02f8fa, there > is no panic at all, so "Fixes:" points to it), but the fact that > backporting e187bc02f8fa to older stable kernels doesn't mean the > fix ("erofs: ensure valid f_path for page cache sharing") need to > be backported to these old kernels too since the page cache sharing > feature won't exist in kernels below 7.0 in any way. > > > > > > There is not any codebase below Linux 7.0 so it's possible to fix > > > 5.15/6.1/6.6/6.12/6.18 in any case. The affected versions are only > > > Linux 7.0+. > > > > Even though e187bc02f8fa ("mm: do file ownership checks with the proper > > mount idmap") was backported to those older trees? > > Yes, it's just impossible to apply "erofs: ensure valid f_path for page > cache sharing" to stable kernels < 7.0 since the feature was introduced > by upstream commit 5ef3208e3be5 ("erofs: introduce the page cache share > feature") [1]. > > [1] https://lwn.net/Articles/1057769/#:~:text=The%20filesystem%20also%20shares%20page%2Dcache%20entries%20for%20identical%20files Ah, that makes more sense. I've fixed this up now and adjusted the "Fixes:" tag to point to the correct commit. The report now looks like: Issue introduced in 7.0 with commit 5ef3208e3be50aa08b4e7a2832f34e16d42c08b3 and fixed in 7.1.8 with commit 3879657c4ffd81b9a42cf575fc6cb60201032587 Issue introduced in 7.0 with commit 5ef3208e3be50aa08b4e7a2832f34e16d42c08b3 and fixed in 7.2 with commit 96b2dbbe58a1ea5df8d29c2fe24b5f04715f4443 thanks, greg k-h