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 6611F4248BA; Fri, 28 Aug 2026 11:30:06 +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=1787916607; cv=none; b=arRZdLF56R6qRBdqe9PEyihrPkfKLuH0rYr3+uspUg4lfbEMHMC+OgpEyUHoD0EsuGyG69LAp4TnQkx/5TNIaTB/ym/QKBFXogvxtyNFE6V2120PZIKLozteh4k5kBUlfJakJ0u1usF7ZTOEL4uU3j4OB29Bg5U9AHKBMKQBsTo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787916607; c=relaxed/simple; bh=C0dYwuadR/kSoQ8AupNWR+F7HR9j/hA7PeKFH4KoRKU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gmivmloEm87BXSG8Khs2JqSZD0tvRsYbkGcrvRZc7squND9xqJkIn9DIdFQ2QaXUhJFTF6FU5BzWm4bBuEsr8rT5S2aTc9eT/sMvqWIN0if2BJCd3Aso6850HaA1MjVS6wmoMcj3nk0fnTRwynd56tsIIx28bEKoCMMfxBFZHmc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b2BkUiKK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b2BkUiKK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 517631F00A3D; Fri, 28 Aug 2026 11:30:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787916606; bh=eXyvllr5AbE0fJ2CdWoEaYoci1UQT9CJTHQ6RVtGnWE=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=b2BkUiKKNtqwTqKmyf3SInJkhE4h6lrX12z4ZA1T+Sla7j6FSTFhBT/PFQ+iycTpx izRa3Eovqh/o4L5O0bWJzQsLftD78HqNOckCMeSg+VNg5fwy2dQp81GmXznLVBbD6K GjjcuiXfelFTjTth3XJVl3IpOKOOoGfyVgam/kJCnsacta3YBG+orNdVPTtJ3de7Q/ DFxrBmmwIoDpeIV7Vb/1/IVeOj7BpiVD59DOsMLxvtRm9Lztwz2cKedLDtLJH8619F pbUw7WHjElyPwoKNeRWNjedZUBE/BLQWN9LlJefcNrjAckXP3BjG6xWHwEWb0RCUnH KpWgCOSuSrm/w== Date: Fri, 28 Aug 2026 19:29:59 +0800 From: Gao Xiang To: Greg KH Cc: 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: Mail-Followup-To: Greg KH , Gao Xiang , cve@kernel.org, linux-kernel@vger.kernel.org, linux-cve-announce@vger.kernel.org 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=utf-8 Content-Disposition: inline In-Reply-To: <2026082849-janitor-stonework-71c9@gregkh> 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 Thanks, Gao Xiang > > thanks, > > greg k-h