From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: "Luis R. Rodriguez" To: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, rusty@rustcorp.com.au, jeyu@redhat.com, "Luis R. Rodriguez" Subject: [PATCH v2] fs: warn in case userspace lied about modprobe return Date: Thu, 1 Jun 2017 11:08:01 -0700 Message-Id: <20170601180801.19827-1-mcgrof@kernel.org> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: kmod <= v19 was broken -- it could return 0 to modprobe calls, incorrectly assuming that a kernel module was built-in, whereas in reality the module was just forming in the kernel. The reason for this is an incorrect userspace heuristics. A userspace kmod fix is available for it [0], however should userspace break again we could go on with an failed get_fs_type() which is hard to debug as the request_module() is detected as returning 0. The first suspect would be that there is something worth with the kernel's module loader and obviously in this case that is not the issue. Since these issues are painful to debug complain when we know userspace has outright lied to us. [0] http://git.kernel.org/cgit/utils/kernel/kmod/kmod.git/commit/libkmod/libkmod-module.c?id=fd44a98ae2eb5eb32161088954ab21e58e19dfc4 Suggested-by: Rusty Russell Cc: Jessica Yu Signed-off-by: Luis R. Rodriguez --- This v2 addresses the ordering issue Jessica pointed out. fs/filesystems.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/filesystems.c b/fs/filesystems.c index cac75547d35c..8b99955e3504 100644 --- a/fs/filesystems.c +++ b/fs/filesystems.c @@ -275,8 +275,10 @@ struct file_system_type *get_fs_type(const char *name) int len = dot ? dot - name : strlen(name); fs = __get_fs_type(name, len); - if (!fs && (request_module("fs-%.*s", len, name) == 0)) + if (!fs && (request_module("fs-%.*s", len, name) == 0)) { fs = __get_fs_type(name, len); + WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name); + } if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) { put_filesystem(fs); -- 2.11.0