linux-kernel - [PATCH AUTOSEL for 4.4 095/162] fs: warn in case userspace lied about modprobe return

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 9 Apr 2018 00:28:54 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Jessica Yu <jeyu@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.4 095/162] fs: warn in case userspace lied about
 modprobe return

From: "Luis R. Rodriguez" <mcgrof@...nel.org>

[ Upstream commit 41124db869b7e00e12052555f8987867ac01d70c ]

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 <rusty@...tcorp.com.au>
Cc: Jessica Yu <jeyu@...hat.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 fs/filesystems.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/filesystems.c b/fs/filesystems.c
index 5797d45a78cb..2a7ae03f821e 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);
-- 
2.15.1