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[net,V2,8/9] net/mlx5e: Use a memory barrier to enforce PTP WQ xmit submission tracking occurs after populating the metadata_map

Message ID 20240302071028.63879-3-saeed@kernel.org (mailing list archive)
State Accepted
Commit b7cf07586c40f926063d4d09f7de28ff82f62b2a
Delegated to: Netdev Maintainers
Headers show
Series [net,V2,1/9] Revert "net/mlx5: Block entering switchdev mode with ns inconsistency" | expand

Checks

Context Check Description
netdev/series_format success Pull request is its own cover letter
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 956 this patch: 956
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 1 maintainers not CCed: richardcochran@gmail.com
netdev/build_clang success Errors and warnings before: 972 this patch: 972
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 972 this patch: 972
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-03-05--03-00 (tests: 890)

Commit Message

Saeed Mahameed March 2, 2024, 7:10 a.m. UTC 
From: Rahul Rameshbabu <rrameshbabu@nvidia.com>

Just simply reordering the functions mlx5e_ptp_metadata_map_put and
mlx5e_ptpsq_track_metadata in the mlx5e_txwqe_complete context is not good
enough since both the compiler and CPU are free to reorder these two
functions. If reordering does occur, the issue that was supposedly fixed by
7e3f3ba97e6c ("net/mlx5e: Track xmit submission to PTP WQ after populating
metadata map") will be seen. This will lead to NULL pointer dereferences in
mlx5e_ptpsq_mark_ts_cqes_undelivered in the NAPI polling context due to the
tracking list being populated before the metadata map.

Fixes: 7e3f3ba97e6c ("net/mlx5e: Track xmit submission to PTP WQ after populating metadata map")
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
CC: Vadim Fedorenko <vadfed@meta.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_tx.c | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index 5c166d9d2dca..2fa076b23fbe 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -401,6 +401,8 @@  mlx5e_txwqe_complete(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 		mlx5e_skb_cb_hwtstamp_init(skb);
 		mlx5e_ptp_metadata_map_put(&sq->ptpsq->metadata_map, skb,
 					   metadata_index);
+		/* ensure skb is put on metadata_map before tracking the index */
+		wmb();
 		mlx5e_ptpsq_track_metadata(sq->ptpsq, metadata_index);
 		if (!netif_tx_queue_stopped(sq->txq) &&
 		    mlx5e_ptpsq_metadata_freelist_empty(sq->ptpsq)) {