]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
Make sure nd->path.mnt and nd->path.dentry are always valid pointers
authorAl Viro <viro@zeniv.linux.org.uk>
Tue, 6 Apr 2021 16:33:07 +0000 (12:33 -0400)
committerAl Viro <viro@zeniv.linux.org.uk>
Tue, 6 Apr 2021 16:33:07 +0000 (12:33 -0400)
commit7d01ef7585c07afaf487759a48486228cd065726
tree32844388a12c3463c659eb7f9915a78261bdbca3
parent7f6c411c9b50cfab41cc798e003eff27608c7016
Make sure nd->path.mnt and nd->path.dentry are always valid pointers

Initialize them in set_nameidata() and make sure that terminate_walk() clears them
once the pointers become potentially invalid (i.e. we leave RCU mode or drop them
in non-RCU one).  Currently we have "path_init() always initializes them and nobody
accesses them outside of path_init()/terminate_walk() segments", which is asking
for trouble.

With that change we would have nd->path.{mnt,dentry}
1) always valid - NULL or pointing to currently allocated objects.
2) non-NULL while we are successfully walking
3) NULL when we are not walking at all
4) contributing to refcounts whenever non-NULL outside of RCU mode.

Fixes: 6c6ec2b0a3e0 ("fs: add support for LOOKUP_CACHED")
Reported-by: syzbot+c88a7030da47945a3cc3@syzkaller.appspotmail.com
Tested-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
fs/namei.c