netdev - [PATCH net v4 2/2] mlx5: fix possible ptp queue fifo use-after-free

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Message-ID: <20230201122605.1350664-3-vadfed@meta.com>
Date:   Wed, 1 Feb 2023 04:26:05 -0800
From:   Vadim Fedorenko <vadfed@...a.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
        Rahul Rameshbabu <rrameshbabu@...dia.com>,
        "Tariq Toukan" <ttoukan.linux@...il.com>,
        Gal Pressman <gal@...dia.com>,
        "Saeed Mahameed" <saeed@...nel.org>
CC:     Vadim Fedorenko <vadfed@...a.com>, <netdev@...r.kernel.org>
Subject: [PATCH net v4 2/2] mlx5: fix possible ptp queue fifo use-after-free

Fifo indexes were not checked during pop operations and it leads to
potential use-after-free when poping from empty queue. Such case was
possible during re-sync action.

There were out-of-order cqe spotted which lead to drain of the queue and
use-after-free because of lack of fifo pointers check. Special check
is added to avoid resync operation if SKB could not exist in the fifo
because of OOO cqe (skb_id must be between consumer and producer index).

Fixes: 58a518948f60 ("net/mlx5e: Add resiliency for PTP TX port timestamp")
Signed-off-by: Vadim Fedorenko <vadfed@...a.com>
---
 .../net/ethernet/mellanox/mlx5/core/en/ptp.c  | 23 ++++++++++++++-----
 .../net/ethernet/mellanox/mlx5/core/en/txrx.h |  4 +++-
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c
index b72de2b520ec..5df726185192 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c
@@ -86,7 +86,7 @@ static bool mlx5e_ptp_ts_cqe_drop(struct mlx5e_ptpsq *ptpsq, u16 skb_cc, u16 skb
 	return (ptpsq->ts_cqe_ctr_mask && (skb_cc != skb_id));
 }
 
-static void mlx5e_ptp_skb_fifo_ts_cqe_resync(struct mlx5e_ptpsq *ptpsq, u16 skb_cc,
+static bool mlx5e_ptp_skb_fifo_ts_cqe_resync(struct mlx5e_ptpsq *ptpsq, u16 skb_cc,
 					     u16 skb_id, int budget)
 {
 	struct skb_shared_hwtstamps hwts = {};
@@ -94,14 +94,23 @@ static void mlx5e_ptp_skb_fifo_ts_cqe_resync(struct mlx5e_ptpsq *ptpsq, u16 skb_
 
 	ptpsq->cq_stats->resync_event++;
 
-	while (skb_cc != skb_id) {
-		skb = mlx5e_skb_fifo_pop(&ptpsq->skb_fifo);
+	if (skb_cc > skb_id || PTP_WQE_CTR2IDX(ptpsq->skb_fifo_pc) < skb_id) {
+		mlx5_core_err_rl(ptpsq->txqsq.mdev, "out-of-order ptp cqe\n");
+		return false;
+	}
+
+	while (skb_cc != skb_id && (skb = mlx5e_skb_fifo_pop(&ptpsq->skb_fifo))) {
 		hwts.hwtstamp = mlx5e_skb_cb_get_hwts(skb)->cqe_hwtstamp;
 		skb_tstamp_tx(skb, &hwts);
 		ptpsq->cq_stats->resync_cqe++;
 		napi_consume_skb(skb, budget);
 		skb_cc = PTP_WQE_CTR2IDX(ptpsq->skb_fifo_cc);
 	}
+
+	if (!skb)
+		return false;
+
+	return true;
 }
 
 static void mlx5e_ptp_handle_ts_cqe(struct mlx5e_ptpsq *ptpsq,
@@ -111,7 +120,7 @@ static void mlx5e_ptp_handle_ts_cqe(struct mlx5e_ptpsq *ptpsq,
 	u16 skb_id = PTP_WQE_CTR2IDX(be16_to_cpu(cqe->wqe_counter));
 	u16 skb_cc = PTP_WQE_CTR2IDX(ptpsq->skb_fifo_cc);
 	struct mlx5e_txqsq *sq = &ptpsq->txqsq;
-	struct sk_buff *skb;
+	struct sk_buff *skb = NULL;
 	ktime_t hwtstamp;
 
 	if (unlikely(MLX5E_RX_ERR_CQE(cqe))) {
@@ -120,8 +129,10 @@ static void mlx5e_ptp_handle_ts_cqe(struct mlx5e_ptpsq *ptpsq,
 		goto out;
 	}
 
-	if (mlx5e_ptp_ts_cqe_drop(ptpsq, skb_cc, skb_id))
-		mlx5e_ptp_skb_fifo_ts_cqe_resync(ptpsq, skb_cc, skb_id, budget);
+	if (mlx5e_ptp_ts_cqe_drop(ptpsq, skb_cc, skb_id) &&
+	    !mlx5e_ptp_skb_fifo_ts_cqe_resync(ptpsq, skb_cc, skb_id, budget)) {
+		goto out;
+	}
 
 	skb = mlx5e_skb_fifo_pop(&ptpsq->skb_fifo);
 	hwtstamp = mlx5e_cqe_ts_to_ns(sq->ptp_cyc2time, sq->clock, get_cqe_ts(cqe));
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h b/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h
index d5afad368a69..e599b86d94b5 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h
@@ -295,13 +295,15 @@ static inline
 void mlx5e_skb_fifo_push(struct mlx5e_skb_fifo *fifo, struct sk_buff *skb)
 {
 	struct sk_buff **skb_item = mlx5e_skb_fifo_get(fifo, (*fifo->pc)++);
-
 	*skb_item = skb;
 }
 
 static inline
 struct sk_buff *mlx5e_skb_fifo_pop(struct mlx5e_skb_fifo *fifo)
 {
+	if (*fifo->pc == *fifo->cc)
+		return NULL;
+
 	return *mlx5e_skb_fifo_get(fifo, (*fifo->cc)++);
 }
 
-- 
2.30.2