From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 13B8216EB63 for ; Mon, 22 Jul 2024 16:34:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721666042; cv=none; b=MkdD26ef9Ar0C0X2Y1bTZIP1rLEycRYUYbdwfI0EvkvkSqmJ3gZq3Pp/TuvcyLOyFTIfpt/ralb8+Ur7lclXPlGYiLMihXw2b05hvQKmyjdCpny/Uax1ygDaSODjLurQoLfxSL42bfgRXSBLG4Q0PG9bm/5J3PmG9Ql1/THYcBQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721666042; c=relaxed/simple; bh=2zErkkCXOo6QAcVxi+vE5cUp0C6FLuFy/WOwkoAGVqg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UEZBTZZRyEnc5/Wx0hgQed8yxBvPpFtd/Gv+Em9j6QGRJDYhBNMRZAh95fTCRqynNg8LOxzhaFxEuFQWmU8hOyTrTED/YuxNne5Q08TO4BmTv/fyTIqcbWzNeoekQIjr2/YKVD3UVCp3GzzGEyG6rTndVWUZ65mLm1Sva8xo55g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CsSfz2wH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="CsSfz2wH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4AE73C32782; Mon, 22 Jul 2024 16:34:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1721666041; bh=2zErkkCXOo6QAcVxi+vE5cUp0C6FLuFy/WOwkoAGVqg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CsSfz2wHfzj9HBw+29N9L8WjgOSO+mfpdaB29XFFVp4wlA6UgDWAx3renpuOO87Fu c4w5NGoOjPOdA+PZnQ+Vuyu+8zSFofsZlmNOe7bxy9S+iW/VZkPBvZnRP3zNJp4nyR FN8UVdomjwl9q9OTTY7FF584r75E+Igt3u0F3jeI= Date: Mon, 22 Jul 2024 18:33:59 +0200 From: Greg KH To: Jann Horn Cc: stable@vger.kernel.org Subject: Re: [PATCH stable 4.19-6.6] filelock: Remove locks reliably when fcntl/close race is detected Message-ID: <2024072249-frostily-palatable-8482@gregkh> References: <20240722142250.155873-1-jannh@google.com> Precedence: bulk X-Mailing-List: stable@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: <20240722142250.155873-1-jannh@google.com> On Mon, Jul 22, 2024 at 04:22:50PM +0200, Jann Horn wrote: > commit 3cad1bc010416c6dd780643476bc59ed742436b9 upstream. > > When fcntl_setlk() races with close(), it removes the created lock with > do_lock_file_wait(). > However, LSMs can allow the first do_lock_file_wait() that created the lock > while denying the second do_lock_file_wait() that tries to remove the lock. > In theory (but AFAIK not in practice), posix_lock_file() could also fail to > remove a lock due to GFP_KERNEL allocation failure (when splitting a range > in the middle). > > After the bug has been triggered, use-after-free reads will occur in > lock_get_status() when userspace reads /proc/locks. This can likely be used > to read arbitrary kernel memory, but can't corrupt kernel memory. > This only affects systems with SELinux / Smack / AppArmor / BPF-LSM in > enforcing mode and only works from some security contexts. > > Fix it by calling locks_remove_posix() instead, which is designed to > reliably get rid of POSIX locks associated with the given file and > files_struct and is also used by filp_flush(). > > Fixes: c293621bbf67 ("[PATCH] stale POSIX lock handling") > Cc: stable@kernel.org > Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2563 > Signed-off-by: Jann Horn > Link: https://lore.kernel.org/r/20240702-fs-lock-recover-2-v1-1-edd456f63789@google.com > Reviewed-by: Jeff Layton > Signed-off-by: Christian Brauner > [stable fixup: ->c.flc_type was ->fl_type in older kernels] > Signed-off-by: Jann Horn > --- > fs/locks.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) Now queued up, thanks. greg k-h