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 EC4FD19D06D; Thu, 25 Jul 2024 14:41:03 +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=1721918464; cv=none; b=FqrBi2AAfPB2Q7QaR1FdtiIoNF3vC9dlxBqRWQFWYni2A1ZAgRdidjQ1PCc2ho1G+idY8ijqwSz1U4zNNY4nZ/Y4RuHBInnANSps4kNQY3GJkYILzbX28lK4/FoxbXd/+9I8hrUz2pwVDjPtqnDYaExLjr4/jpmMSKiXSnaZca0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721918464; c=relaxed/simple; bh=SUyyXiUq/pAc17sOmRuSBYOfrAsHvdInMkQFr2K2ZMc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IbRnUGRiWgSOQiuus+cipBa7qrVPlLpJrPc1RZNnsHjqA7rohqQh9w5EML/kU/B0EH8FBBdETJNwp14bo4jVlUxiCJWytRlYAYcF8v0n29q14h6PEU5fc2uNjWg7i1bnFlW9Tc6vKjseB9tY4wevMar5Vgq+XbAhqiquv4qQL9E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=fyWkNhL1; 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="fyWkNhL1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BC5BC4AF0F; Thu, 25 Jul 2024 14:41:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1721918463; bh=SUyyXiUq/pAc17sOmRuSBYOfrAsHvdInMkQFr2K2ZMc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fyWkNhL1iUrkgf/0hxnSDDv83YakMQVyQ6pd3vKQoViduWkM+FidEkEDO8QX6wd29 B0wHNWTUmXw8IaKRChO4u91/9pXN2AlTNqUbFLet69cb7vpH1KmIEdXXsi4s0ErCXQ KxzhCvovUbZyArivXxa2Q0c8zPJNgVdeLKMSWnPQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, Jann Horn , Jeff Layton , Christian Brauner Subject: [PATCH 4.19 27/33] filelock: Remove locks reliably when fcntl/close race is detected Date: Thu, 25 Jul 2024 16:36:50 +0200 Message-ID: <20240725142729.535353711@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240725142728.511303502@linuxfoundation.org> References: <20240725142728.511303502@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn 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 Signed-off-by: Greg Kroah-Hartman --- fs/locks.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/fs/locks.c +++ b/fs/locks.c @@ -2297,8 +2297,9 @@ int fcntl_setlk(unsigned int fd, struct error = do_lock_file_wait(filp, cmd, file_lock); /* - * Attempt to detect a close/fcntl race and recover by releasing the - * lock that was just acquired. There is no need to do that when we're + * Detect close/fcntl races and recover by zapping all POSIX locks + * associated with this file and our files_struct, just like on + * filp_flush(). There is no need to do that when we're * unlocking though, or for OFD locks. */ if (!error && file_lock->fl_type != F_UNLCK && @@ -2312,9 +2313,7 @@ int fcntl_setlk(unsigned int fd, struct f = fcheck(fd); spin_unlock(¤t->files->file_lock); if (f != filp) { - file_lock->fl_type = F_UNLCK; - error = do_lock_file_wait(filp, cmd, file_lock); - WARN_ON_ONCE(error); + locks_remove_posix(filp, ¤t->files); error = -EBADF; } }