From: Eric Biggers <ebiggers@kernel.org>
To: linux-fsdevel@vger.kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: [PATCH] vfs: move_mount: reject moving kernel internal mounts
Date: Sat, 29 Jun 2019 13:27:44 -0700 [thread overview]
Message-ID: <20190629202744.12396-1-ebiggers@kernel.org> (raw)
In-Reply-To: <CACT4Y+ZN8CZq7L1GQANr25extEqPASRERGVh+sD4-55cvWPOSg@mail.gmail.com>
From: Eric Biggers <ebiggers@google.com>
sys_move_mount() crashes by dereferencing the pointer MNT_NS_INTERNAL,
a.k.a. ERR_PTR(-EINVAL), if the old mount is specified by fd for a
kernel object with an internal mount, such as a pipe or memfd.
Fix it by checking for this case and returning -EINVAL.
Reproducer:
#include <unistd.h>
#define __NR_move_mount 429
#define MOVE_MOUNT_F_EMPTY_PATH 0x00000004
int main()
{
int fds[2];
pipe(fds);
syscall(__NR_move_mount, fds[0], "", -1, "/", MOVE_MOUNT_F_EMPTY_PATH);
}
Reported-by: syzbot+6004acbaa1893ad013f0@syzkaller.appspotmail.com
Fixes: 2db154b3ea8e ("vfs: syscall: Add move_mount(2) to move mounts around")
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/namespace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 7660c2749c96..a7e5a44770a7 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2600,7 +2600,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
if (attached && !check_mnt(old))
goto out;
- if (!attached && !(ns && is_anon_ns(ns)))
+ if (!attached && !(ns && ns != MNT_NS_INTERNAL && is_anon_ns(ns)))
goto out;
if (old->mnt.mnt_flags & MNT_LOCKED)
--
2.22.0
next prev parent reply other threads:[~2019-06-29 20:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-18 10:47 general protection fault in do_move_mount (2) syzbot
2019-06-18 14:02 ` Al Viro
2019-06-24 9:28 ` Dmitry Vyukov
2019-06-29 20:27 ` Eric Biggers [this message]
2019-06-29 20:39 ` [PATCH] vfs: move_mount: reject moving kernel internal mounts Al Viro
2019-07-01 1:08 ` Al Viro
2019-07-01 15:43 ` Eric Biggers
2019-07-01 7:38 ` David Howells
2019-07-01 11:19 ` Al Viro
2019-07-01 16:45 ` Eric Biggers
2019-07-01 18:22 ` Al Viro
2019-07-01 19:20 ` Al Viro
2019-07-02 18:22 ` Eric Biggers
2019-07-09 19:40 ` Eric Biggers
2019-07-09 20:54 ` Al Viro
2019-07-10 3:23 ` 6 new syscalls without tests (was: [PATCH] vfs: move_mount: reject moving kernel internal mounts) Eric Biggers
2019-07-05 9:01 ` move_mount.2 David Howells
2019-06-29 20:39 ` general protection fault in do_move_mount (2) Eric Biggers
2019-07-01 14:59 ` Dmitry Vyukov
2019-07-01 15:18 ` Eric Biggers
2019-07-05 12:17 ` Dmitry Vyukov
2019-07-05 13:02 ` Dmitry Vyukov
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