On Thu, Jun 7, 2018 at 2:26 PM, Al Viro <v...@zeniv.linux.org.uk> wrote: > On Thu, Jun 07, 2018 at 01:39:49PM -0700, Cong Wang wrote: >> fchownat() doesn't even hold refcnt of fd until it figures out >> fd is really needed (otherwise is ignored) and releases it after >> it resolves the path. This means sock_close() could race with >> sockfs_setattr(), which leads to a NULL pointer dereference >> since typically we set sock->sk to NULL in ->release(). >> >> As pointed out by Al, this is unique to sockfs. So we can fix this >> in socket layer by acquiring inode_lock in sock_close() and >> checking against NULL in sockfs_setattr(). > > That looks like a massive overkill - it's way heavier than it should be.
I don't see any other quick way to fix this. My initial thought is to keep that refcnt until path_put(), apparently you don't like it either. > And it's very likely to trigger shitloads of deadlock warnings, some > possibly even true. I do audit the inode_lock usage in networking, I don't see any deadlock, of course, there could be some non-networking code uses socket API that I missed. But _generally_, socket doesn't have a pointer to retrieve this inode.
