5.15-stable review patch. If anyone has any objections, please let me know.
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From: Magnus Karlsson magnus.karlsson@intel.com
[ Upstream commit 3e019d8a05a38abb5c85d4f1e85fda964610aa14 ]
Fix a use-after-free error that is possible if the xsk_diag interface is used after the socket has been unbound from the device. This can happen either due to the socket being closed or the device disappearing. In the early days of AF_XDP, the way we tested that a socket was not bound to a device was to simply check if the netdevice pointer in the xsk socket structure was NULL. Later, a better system was introduced by having an explicit state variable in the xsk socket struct. For example, the state of a socket that is on the way to being closed and has been unbound from the device is XSK_UNBOUND.
The commit in the Fixes tag below deleted the old way of signalling that a socket is unbound, setting dev to NULL. This in the belief that all code using the old way had been exterminated. That was unfortunately not true as the xsk diagnostics code was still using the old way and thus does not work as intended when a socket is going down. Fix this by introducing a test against the state variable. If the socket is in the state XSK_UNBOUND, simply abort the diagnostic's netlink operation.
Fixes: 18b1ab7aa76b ("xsk: Fix race at socket teardown") Reported-by: syzbot+822d1359297e2694f873@syzkaller.appspotmail.com Signed-off-by: Magnus Karlsson magnus.karlsson@intel.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Tested-by: syzbot+822d1359297e2694f873@syzkaller.appspotmail.com Tested-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Reviewed-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Link: https://lore.kernel.org/bpf/20230831100119.17408-1-magnus.karlsson@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/xdp/xsk_diag.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/net/xdp/xsk_diag.c b/net/xdp/xsk_diag.c index c014217f5fa7d..22b36c8143cfd 100644 --- a/net/xdp/xsk_diag.c +++ b/net/xdp/xsk_diag.c @@ -111,6 +111,9 @@ static int xsk_diag_fill(struct sock *sk, struct sk_buff *nlskb, sock_diag_save_cookie(sk, msg->xdiag_cookie);
mutex_lock(&xs->mutex); + if (READ_ONCE(xs->state) == XSK_UNBOUND) + goto out_nlmsg_trim; + if ((req->xdiag_show & XDP_SHOW_INFO) && xsk_diag_put_info(xs, nlskb)) goto out_nlmsg_trim;