On Tue, 2022-05-03 at 14:17 -0700, Eric Dumazet wrote: > On Tue, May 3, 2022 at 4:40 AM <patchwork-bot+netdevbpf@xxxxxxxxxx> wrote: > > > > Hello: > > > > This patch was applied to netdev/net.git (master) > > by Paolo Abeni <pabeni@xxxxxxxxxx>: > > > > On Mon, 2 May 2022 10:40:18 +0900 you wrote: > > > syzbot is reporting use-after-free read in tcp_retransmit_timer() [1], > > > for TCP socket used by RDS is accessing sock_net() without acquiring a > > > refcount on net namespace. Since TCP's retransmission can happen after > > > a process which created net namespace terminated, we need to explicitly > > > acquire a refcount. > > > > > > Link: https://syzkaller.appspot.com/bug?extid=694120e1002c117747ed [1] > > > Reported-by: syzbot <syzbot+694120e1002c117747ed@xxxxxxxxxxxxxxxxxxxxxxxxx> > > > Fixes: 26abe14379f8e2fa ("net: Modify sk_alloc to not reference count the netns of kernel sockets.") > > > Fixes: 8a68173691f03661 ("net: sk_clone_lock() should only do get_net() if the parent is not a kernel socket") > > > Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> > > > Tested-by: syzbot <syzbot+694120e1002c117747ed@xxxxxxxxxxxxxxxxxxxxxxxxx> > > > > > > [...] > > > > Here is the summary with links: > > - [v2] net: rds: acquire refcount on TCP sockets > > https://git.kernel.org/netdev/net/c/3a58f13a881e > > > > You are awesome, thank you! > > -- > > Deet-doot-dot, I am a bot. > > https://korg.docs.kernel.org/patchwork/pwbot.html > > > > > > I think we merged this patch too soon. My fault. > My question is : What prevents rds_tcp_conn_path_connect(), and thus > rds_tcp_tune() to be called > after the netns refcount already reached 0 ? > > I guess we can wait for next syzbot report, but I think that get_net() > should be replaced > by maybe_get_net() > Should we revert this patch before the next pull request, if a suitable incremental fix is not available by then? It looks like the window of opportunity for the race is roughly the same? Thanks! Paolo
