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b=ldiKvQql6bj+j7UtmDeRgNi75i txxy61Zr866uf+AzRzCueP5rd1WZw5wEgLO2CYlXHOCQCNf5qY9Jnqb3voZuq2oenFe/JdH4CzAFk 67Me9Is1PjYnPGNMd1J3UPtWh2Gu8TNUPtLo/W7wppiisKBoSEDoAiD/+dv0Tl3QeDOA=; Received: from dfw.source.kernel.org ([139.178.84.217]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1sbeyz-0004iP-RG for linux-f2fs-devel@lists.sourceforge.net; Wed, 07 Aug 2024 11:37:34 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 7C79E61257; Wed, 7 Aug 2024 11:37:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FBAAC32782; Wed, 7 Aug 2024 11:37:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723030643; bh=f36Eut4cpuTeN/nHR83eH313AyJ5JQ3s2RGRYRnZE2U=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=U5BQyklxnmNN5PAXzuPelTAWieKNWfAsDmMIfL6P1mZ1nq+oy7hBxwu7BgG6CW0Cf MANwNVDDKlb+/RtVlrjpxcyVAWb8UCkDS17WsJwjB2JFDb7gsmFpSu5zEeABoAk+uh LY5lkJfGKMIYcBixGENYZT9XAqoNlArnLzpOEv4xfF5s0RE9Z1o87t/AqT/J8OKPbr 7faYb3lVH4mef0qPvRQvjDjru+nbiAYdM2UuGR+qerm1kgcB1U9eTx0HDDto0dcu7/ 9Tgx5fzaAc+nRxG23Tn9Bf8QSWiFCRvRNda7pD9chEFE22oPcTk+lsTOwHs73W9auG ybhnGmm9Y2Lxw== Message-ID: <0892524d-e9c1-4b27-8622-11cd697451ea@kernel.org> Date: Wed, 7 Aug 2024 19:37:22 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Jann Horn , Jaegeuk Kim References: <20240806-f2fs-atomic-write-v1-1-8a586e194fd7@google.com> Content-Language: en-US From: Chao Yu Autocrypt: addr=chao@kernel.org; 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charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2024/8/6 22:07, Jann Horn wrote: > The F2FS ioctls for starting and committing atomic writes check for > inode_owner_or_capable(), but this does not give LSMs like SELinux or > Landlock an opportunity to deny the write access - if the caller's FSUID > matches the inode's UID, inode_owner_or_capable() immediately returns true. > > There are scenarios where LSMs want to deny a process the ability to write > particular files, even files that the FSUID of the process owns; but this > can currently partially be bypassed using atomic write ioctls in two ways: > > - F2FS_IOC_START_ATOMIC_REPLACE + F2FS_IOC_COMMIT_ATOMIC_WRITE can > truncate an inode to size 0 > - F2FS_IOC_START_ATOMIC_WRITE + F2FS_IOC_ABORT_ATOMIC_WRITE can revert > changes another process concurrently made to a file > > Fix it by requiring FMODE_WRITE for these operations, just like for > F2FS_IOC_MOVE_RANGE. Since any legitimate caller should only be using these > ioctls when intending to write into the file, that seems unlikely to break > anything. > > Fixes: 88b88a667971 ("f2fs: support atomic writes") > Cc: stable@vger.kernel.org > Signed-off-by: Jann Horn Reviewed-by: Chao Yu Thanks, _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel