Commit 1b0b9cc8 authored Jun 12, 2019 by Eric Biggers Committed by Al Viro Jun 17, 2019

vfs: fsmount: add missing mntget()

sys_fsmount() needs to take a reference to the new mount when adding it
to the anonymous mount namespace. Otherwise the filesystem can be
unmounted while it's still in use, as found by syzkaller.

Reported-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: <syzbot+99de05d099a170867f22@syzkaller.appspotmail.com>
Reported-by: <syzbot+7008b8b8ba7df475fdc8@syzkaller.appspotmail.com>
Fixes: 93766fbd ("vfs: syscall: Add fsmount() to create a mount for a superblock")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent 9e0babf2

fs/namespace.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -3445,6 +3445,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
		ns->root = mnt;
		ns->mounts = 1;
		list_add(&mnt->mnt_list, &ns->list);
		mntget(newmount.mnt);

		/* Attach to an apparent O_PATH fd with a note that we need to unmount
		* it, not just simply put it.