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 <[email protected]> Reported-by: [email protected] Reported-by: [email protected] Fixes: 93766fb ("vfs: syscall: Add fsmount() to create a mount for a superblock") Signed-off-by: Eric Biggers <[email protected]> Signed-off-by: Al Viro <[email protected]>
jb55 · Jun 17, 2019 · 1b0b9cc · 1b0b9cc
1 parent 9e0babf
commit 1b0b9cc
Showing 1 changed file with 1 addition and 0 deletions.
diff --git a/fs/namespace.c b/fs/namespace.c
@@ -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.