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 ECFC81C07ED; Tue, 15 Oct 2024 13:10:09 +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=1728997810; cv=none; b=h5stD67/++Uzzgsmsny/7r36Zwx7/NiUWIyY+NQkpY9YCKQ8frG+SUYi+E3niZCc+dLEYzpHau/+uTQ1/kVAMcLFp340mR0dLY9KV96Tj5FMteOEqvo/ymoWT9yHdlngH7ORSjJ7PQBR5LE68aKmUd2VEXVN7vHFuA8h8PIdd2A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728997810; c=relaxed/simple; bh=qHy66VAQahBgRbnCLfA+fK/fy2r8cOTkVnM9PivXteE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AmlaL7izEAdLa7D3ydEGDLqW0Ob5p6fXvCSEAGWx3onZXnMWPri0GJMmezW0Z0qC6aHtein2nZvGqylss1o3W/i5flt4KL0Qbz5F+YGa0VebsG9o1LFD8UexSYSIaOCEYgMCjMHuEuokCftw8JucIMX01A/5cu8HI4EatB3+TLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NTt8J3UK; 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="NTt8J3UK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E109C4CEC6; Tue, 15 Oct 2024 13:10:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1728997809; bh=qHy66VAQahBgRbnCLfA+fK/fy2r8cOTkVnM9PivXteE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NTt8J3UK0bxUoofVjJretJuzF6g1EXoVfUhqk6HA4TCQ+9jDhB9fh8Bu6M5eCekoB 90cA904ZPyvyCz7tKBZpwdSX+clOrY9fJ/H3LvUbbAsAaqRfEv/dBUGySypL12j9Ii /NtkPeIy7tfWanc49ZSjB9Q3o65amDhQOt8Rr5IQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jann Horn , Chao Yu , Eric Biggers , Jaegeuk Kim , Sasha Levin Subject: [PATCH 5.10 293/518] f2fs: Require FMODE_WRITE for atomic write ioctls Date: Tue, 15 Oct 2024 14:43:17 +0200 Message-ID: <20241015123928.294802984@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241015123916.821186887@linuxfoundation.org> References: <20241015123916.821186887@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit 4f5a100f87f32cb65d4bb1ad282a08c92f6f591e upstream. 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 Reviewed-by: Eric Biggers Signed-off-by: Jaegeuk Kim Signed-off-by: Eric Biggers Signed-off-by: Sasha Levin --- fs/f2fs/file.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 060bd64502c68..7ce22137afbe9 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2054,6 +2054,9 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) struct f2fs_sb_info *sbi = F2FS_I_SB(inode); int ret; + if (!(filp->f_mode & FMODE_WRITE)) + return -EBADF; + if (!inode_owner_or_capable(inode)) return -EACCES; @@ -2124,6 +2127,9 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp) struct inode *inode = file_inode(filp); int ret; + if (!(filp->f_mode & FMODE_WRITE)) + return -EBADF; + if (!inode_owner_or_capable(inode)) return -EACCES; @@ -2166,6 +2172,9 @@ static int f2fs_ioc_start_volatile_write(struct file *filp) struct inode *inode = file_inode(filp); int ret; + if (!(filp->f_mode & FMODE_WRITE)) + return -EBADF; + if (!inode_owner_or_capable(inode)) return -EACCES; @@ -2201,6 +2210,9 @@ static int f2fs_ioc_release_volatile_write(struct file *filp) struct inode *inode = file_inode(filp); int ret; + if (!(filp->f_mode & FMODE_WRITE)) + return -EBADF; + if (!inode_owner_or_capable(inode)) return -EACCES; @@ -2230,6 +2242,9 @@ static int f2fs_ioc_abort_volatile_write(struct file *filp) struct inode *inode = file_inode(filp); int ret; + if (!(filp->f_mode & FMODE_WRITE)) + return -EBADF; + if (!inode_owner_or_capable(inode)) return -EACCES; -- 2.43.0