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Message-ID: <aYSeb42KRzlc4SbA@boxer>
Date: Thu, 5 Feb 2026 14:43:11 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Keita Morisaki <kmta1236@...il.com>
CC: <tony.nguyen@...el.com>, <przemyslaw.kitszel@...el.com>,
<andrew+netdev@...n.ch>, <davem@...emloft.net>, <edumazet@...gle.com>,
<kuba@...nel.org>, <pabeni@...hat.com>, <paul.greenwalt@...el.com>,
<aleksandr.loktionov@...el.com>, <alice.michael@...el.com>,
<intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] ice: fix race condition in TX timestamp ring cleanup
On Thu, Feb 05, 2026 at 11:43:27AM +0900, Keita Morisaki wrote:
> Fix a race condition between ice_free_tx_tstamp_ring() and ice_tx_map()
> that can cause a NULL pointer dereference.
>
> ice_free_tx_tstamp_ring currently clears the ICE_TX_FLAGS_TXTIME flag
> after NULLing the tstamp_ring. This could allow a concurrent ice_tx_map
> call on another CPU to dereference the tstamp_ring, which could lead to
> a NULL pointer dereference.
>
> CPU A:ice_free_tx_tstamp_ring() | CPU B:ice_tx_map()
> --------------------------------|---------------------------------
> tx_ring->tstamp_ring = NULL |
> | ice_is_txtime_cfg() -> true
> | tstamp_ring = tx_ring->tstamp_ring
> | tstamp_ring->count // NULL deref!
> flags &= ~ICE_TX_FLAGS_TXTIME |
>
> Fix by:
> 1. Reordering ice_free_tx_tstamp_ring() to clear the flag before
> NULLing the pointer, with smp_wmb() to ensure proper ordering.
> 2. Adding smp_rmb() in ice_tx_map() after the flag check to order the
> flag read before the pointer read, using READ_ONCE() for the
> pointer, and adding a NULL check as a safety net.
> 3. Converting tx_ring->flags from u8 to DECLARE_BITMAP() and using
> atomic bitops (set_bit(), clear_bit(), test_bit()) for all flag
> operations throughout the driver:
> - ICE_TX_RING_FLAGS_XDP
> - ICE_TX_RING_FLAGS_VLAN_L2TAG1
> - ICE_TX_RING_FLAGS_VLAN_L2TAG2
> - ICE_TX_RING_FLAGS_TXTIME
Hi Keita,
am I reading this right or you only modified flags to be bitmap on Tx side
and Rx is left as-is?
Would be nice to reflect this on Rx side as well, but I know it is out of
the scope for this patch.
Would you like to do a follow-up patch for that which would be sent to
-next tree?
Also your patch should contain the tree you are dedicating your work:
[PATCH net v2] ice: fix race condition in TX timestamp ring cleanup
As for rest of the stuff it makes sense to me, however best if Paul could
give his ack here.
>
> Fixes: ccde82e909467 ("ice: add E830 Earliest TxTime First Offload support")
> Signed-off-by: Keita Morisaki <kmta1236@...il.com>
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@...el.com>
> ---
> Changes in v2:
> - Convert tx_ring->flags from u8 to DECLARE_BITMAP() and use atomic
> bitops (set_bit(), clear_bit(), test_bit()) for all flag operations
> instead of WRITE_ONCE() for flag updates
> - Rename flags from ICE_TX_FLAGS_RING_* to ICE_TX_RING_FLAGS_* to
> distinguish from per-packet flags (ICE_TX_FLAGS_*)
>
> drivers/net/ethernet/intel/ice/ice.h | 4 ++--
> drivers/net/ethernet/intel/ice/ice_dcb_lib.c | 2 +-
> drivers/net/ethernet/intel/ice/ice_lib.c | 4 ++--
> drivers/net/ethernet/intel/ice/ice_txrx.c | 23 ++++++++++++++------
> drivers/net/ethernet/intel/ice/ice_txrx.h | 16 +++++++++-----
> 5 files changed, 31 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
> index 00f75d87c73f9..5baeca824cd99 100644
> --- a/drivers/net/ethernet/intel/ice/ice.h
> +++ b/drivers/net/ethernet/intel/ice/ice.h
> @@ -753,7 +753,7 @@ static inline bool ice_is_xdp_ena_vsi(struct ice_vsi *vsi)
>
> static inline void ice_set_ring_xdp(struct ice_tx_ring *ring)
> {
> - ring->flags |= ICE_TX_FLAGS_RING_XDP;
> + set_bit(ICE_TX_RING_FLAGS_XDP, ring->flags);
> }
>
> /**
> @@ -778,7 +778,7 @@ static inline bool ice_is_txtime_ena(const struct ice_tx_ring *ring)
> */
> static inline bool ice_is_txtime_cfg(const struct ice_tx_ring *ring)
> {
> - return !!(ring->flags & ICE_TX_FLAGS_TXTIME);
> + return test_bit(ICE_TX_RING_FLAGS_TXTIME, ring->flags);
> }
>
> /**
> diff --git a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> index 9fc8681cc58ea..bd74344271f3f 100644
> --- a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> @@ -943,7 +943,7 @@ ice_tx_prepare_vlan_flags_dcb(struct ice_tx_ring *tx_ring,
> /* if this is not already set it means a VLAN 0 + priority needs
> * to be offloaded
> */
> - if (tx_ring->flags & ICE_TX_FLAGS_RING_VLAN_L2TAG2)
> + if (test_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG2, tx_ring->flags))
> first->tx_flags |= ICE_TX_FLAGS_HW_OUTER_SINGLE_VLAN;
> else
> first->tx_flags |= ICE_TX_FLAGS_HW_VLAN;
> diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
> index d47af94f31a99..55ff0708d136e 100644
> --- a/drivers/net/ethernet/intel/ice/ice_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_lib.c
> @@ -1412,9 +1412,9 @@ static int ice_vsi_alloc_rings(struct ice_vsi *vsi)
> ring->count = vsi->num_tx_desc;
> ring->txq_teid = ICE_INVAL_TEID;
> if (dvm_ena)
> - ring->flags |= ICE_TX_FLAGS_RING_VLAN_L2TAG2;
> + set_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG2, ring->flags);
> else
> - ring->flags |= ICE_TX_FLAGS_RING_VLAN_L2TAG1;
> + set_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG1, ring->flags);
> WRITE_ONCE(vsi->tx_rings[i], ring);
> }
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
> index ad76768a42323..564e4e33ecbc3 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> @@ -190,9 +190,10 @@ void ice_free_tstamp_ring(struct ice_tx_ring *tx_ring)
> void ice_free_tx_tstamp_ring(struct ice_tx_ring *tx_ring)
> {
> ice_free_tstamp_ring(tx_ring);
> + clear_bit(ICE_TX_RING_FLAGS_TXTIME, tx_ring->flags);
> + smp_wmb(); /* order flag clear before pointer NULL */
> kfree_rcu(tx_ring->tstamp_ring, rcu);
> - tx_ring->tstamp_ring = NULL;
> - tx_ring->flags &= ~ICE_TX_FLAGS_TXTIME;
> + WRITE_ONCE(tx_ring->tstamp_ring, NULL);
> }
>
> /**
> @@ -405,7 +406,7 @@ static int ice_alloc_tstamp_ring(struct ice_tx_ring *tx_ring)
> tx_ring->tstamp_ring = tstamp_ring;
> tstamp_ring->desc = NULL;
> tstamp_ring->count = ice_calc_ts_ring_count(tx_ring);
> - tx_ring->flags |= ICE_TX_FLAGS_TXTIME;
> + set_bit(ICE_TX_RING_FLAGS_TXTIME, tx_ring->flags);
> return 0;
> }
>
> @@ -1519,13 +1520,20 @@ ice_tx_map(struct ice_tx_ring *tx_ring, struct ice_tx_buf *first,
> return;
>
> if (ice_is_txtime_cfg(tx_ring)) {
> - struct ice_tstamp_ring *tstamp_ring = tx_ring->tstamp_ring;
> - u32 tstamp_count = tstamp_ring->count;
> - u32 j = tstamp_ring->next_to_use;
> + struct ice_tstamp_ring *tstamp_ring;
> + u32 tstamp_count, j;
> struct ice_ts_desc *ts_desc;
> struct timespec64 ts;
> u32 tstamp;
>
> + smp_rmb(); /* order flag read before pointer read */
> + tstamp_ring = READ_ONCE(tx_ring->tstamp_ring);
> + if (unlikely(!tstamp_ring))
> + goto ring_kick;
> +
> + tstamp_count = tstamp_ring->count;
> + j = tstamp_ring->next_to_use;
> +
> ts = ktime_to_timespec64(first->skb->tstamp);
> tstamp = ts.tv_nsec >> ICE_TXTIME_CTX_RESOLUTION_128NS;
>
> @@ -1553,6 +1561,7 @@ ice_tx_map(struct ice_tx_ring *tx_ring, struct ice_tx_buf *first,
> tstamp_ring->next_to_use = j;
> writel_relaxed(j, tstamp_ring->tail);
> } else {
> +ring_kick:
> writel_relaxed(i, tx_ring->tail);
> }
> return;
> @@ -1812,7 +1821,7 @@ ice_tx_prepare_vlan_flags(struct ice_tx_ring *tx_ring, struct ice_tx_buf *first)
> */
> if (skb_vlan_tag_present(skb)) {
> first->vid = skb_vlan_tag_get(skb);
> - if (tx_ring->flags & ICE_TX_FLAGS_RING_VLAN_L2TAG2)
> + if (test_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG2, tx_ring->flags))
> first->tx_flags |= ICE_TX_FLAGS_HW_OUTER_SINGLE_VLAN;
> else
> first->tx_flags |= ICE_TX_FLAGS_HW_VLAN;
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
> index e440c55d9e9f0..d35ffdc3dc84d 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.h
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
> @@ -181,6 +181,14 @@ enum ice_rx_dtype {
> ICE_RX_DTYPE_SPLIT_ALWAYS = 2,
> };
>
> +enum ice_tx_ring_flags {
> + ICE_TX_RING_FLAGS_XDP,
> + ICE_TX_RING_FLAGS_VLAN_L2TAG1,
> + ICE_TX_RING_FLAGS_VLAN_L2TAG2,
> + ICE_TX_RING_FLAGS_TXTIME,
> + ICE_TX_RING_FLAGS_NBITS,
> +};
> +
> struct ice_pkt_ctx {
> u64 cached_phctime;
> __be16 vlan_proto;
> @@ -333,11 +341,7 @@ struct ice_tx_ring {
> u32 txq_teid; /* Added Tx queue TEID */
> /* CL4 - 4th cacheline starts here */
> struct ice_tstamp_ring *tstamp_ring;
> -#define ICE_TX_FLAGS_RING_XDP BIT(0)
> -#define ICE_TX_FLAGS_RING_VLAN_L2TAG1 BIT(1)
> -#define ICE_TX_FLAGS_RING_VLAN_L2TAG2 BIT(2)
> -#define ICE_TX_FLAGS_TXTIME BIT(3)
> - u8 flags;
> + DECLARE_BITMAP(flags, ICE_TX_RING_FLAGS_NBITS);
> u8 dcb_tc; /* Traffic class of ring */
> u16 quanta_prof_id;
> } ____cacheline_internodealigned_in_smp;
> @@ -349,7 +353,7 @@ static inline bool ice_ring_ch_enabled(struct ice_tx_ring *ring)
>
> static inline bool ice_ring_is_xdp(struct ice_tx_ring *ring)
> {
> - return !!(ring->flags & ICE_TX_FLAGS_RING_XDP);
> + return test_bit(ICE_TX_RING_FLAGS_XDP, ring->flags);
> }
>
> enum ice_container_type {
>
> base-commit: 18f7fcd5e69a04df57b563360b88be72471d6b62
> --
> 2.34.1
>
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