On Thu, Nov 30, 2023 at 4:54 PM John Fastabend <john.fastabend@xxxxxxxxx> wrote: > > Daniel Borkmann wrote: > > On 11/30/23 3:53 PM, Eric Dumazet wrote: > > > On Thu, Nov 30, 2023 at 12:49 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: > > >> > > >> Hi David, hi Jakub, hi Paolo, hi Eric, > > >> > > >> The following pull-request contains BPF updates for your *net* tree. > > >> > > >> We've added 5 non-merge commits during the last 7 day(s) which contain > > >> a total of 10 files changed, 66 insertions(+), 15 deletions(-). > > >> > > >> The main changes are: > > >> > > >> 1) Fix AF_UNIX splat from use after free in BPF sockmap, from John Fastabend. > > > > > > syzbot is not happy with this patch. > > > > > > Would the following fix make sense? > > > > > > diff --git a/net/unix/unix_bpf.c b/net/unix/unix_bpf.c > > > index 7ea7c3a0d0d06224f49ad5f073bf772b9528a30a..58e89361059fbf9d5942c6dd268dd80ac4b57098 > > > 100644 > > > --- a/net/unix/unix_bpf.c > > > +++ b/net/unix/unix_bpf.c > > > @@ -168,7 +168,8 @@ int unix_stream_bpf_update_proto(struct sock *sk, > > > struct sk_psock *psock, bool r > > > } > > > > > > sk_pair = unix_peer(sk); > > > - sock_hold(sk_pair); > > > + if (sk_pair) > > > + sock_hold(sk_pair); > > > psock->sk_pair = sk_pair; > > > unix_stream_bpf_check_needs_rebuild(psock->sk_proto); > > > sock_replace_proto(sk, &unix_stream_bpf_prot); > > > > > > > Oh well :/ Above looks reasonable to me, thanks, but I'll defer to John & Jakub (both Cc'ed) > > for a final look. > > > > Thanks, > > Daniel > > Is that sk in LISTEN state by any chance? I can't think why we even allow such a > thing for af_unix sockets. Another possible fix would be to block adding these > to sockmap at all. > > But, above should be fine as well so I would just go with that. Eric or Daniel > would you like to submit a patch or I can if needed. Here is the repro: # See https://goo.gl/kgGztJ for information about syzkaller reproducers. #{"procs":1,"slowdown":1,"sandbox":"","sandbox_arg":0,"close_fds":false} r0 = socket(0x1, 0x1, 0x0) r1 = bpf$MAP_CREATE(0x0, &(0x7f0000000200)=@base={0xf, 0x4, 0x4, 0x12}, 0x48) bpf$MAP_UPDATE_ELEM(0x2, &(0x7f0000000140)={r1, &(0x7f0000000000), &(0x7f0000000100)=@tcp6=r0}, 0x20) I will release the syzbot report, and send the patch, thanks.
