6.10-stable review patch. If anyone has any objections, please let me know.
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From: Stanislav Fomichev sdf@fomichev.me
[ Upstream commit d5e726d9143c5624135f5dc9e4069799adeef734 ]
Julian reports that commit 341ac980eab9 ("xsk: Support tx_metadata_len") can break existing use cases which don't zero-initialize xdp_umem_reg padding. Introduce new XDP_UMEM_TX_METADATA_LEN to make sure we interpret the padding as tx_metadata_len only when being explicitly asked.
Fixes: 341ac980eab9 ("xsk: Support tx_metadata_len") Reported-by: Julian Schindel mail@arctic-alpaca.de Signed-off-by: Stanislav Fomichev sdf@fomichev.me Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Link: https://lore.kernel.org/bpf/20240713015253.121248-2-sdf@fomichev.me Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/networking/xsk-tx-metadata.rst | 16 ++++++++++------ include/uapi/linux/if_xdp.h | 4 ++++ net/xdp/xdp_umem.c | 9 ++++++--- 3 files changed, 20 insertions(+), 9 deletions(-)
diff --git a/Documentation/networking/xsk-tx-metadata.rst b/Documentation/networking/xsk-tx-metadata.rst index bd033fe95cca5..e76b0cfc32f7d 100644 --- a/Documentation/networking/xsk-tx-metadata.rst +++ b/Documentation/networking/xsk-tx-metadata.rst @@ -11,12 +11,16 @@ metadata on the receive side. General Design ==============
-The headroom for the metadata is reserved via ``tx_metadata_len`` in -``struct xdp_umem_reg``. The metadata length is therefore the same for -every socket that shares the same umem. The metadata layout is a fixed UAPI, -refer to ``union xsk_tx_metadata`` in ``include/uapi/linux/if_xdp.h``. -Thus, generally, the ``tx_metadata_len`` field above should contain -``sizeof(union xsk_tx_metadata)``. +The headroom for the metadata is reserved via ``tx_metadata_len`` and +``XDP_UMEM_TX_METADATA_LEN`` flag in ``struct xdp_umem_reg``. The metadata +length is therefore the same for every socket that shares the same umem. +The metadata layout is a fixed UAPI, refer to ``union xsk_tx_metadata`` in +``include/uapi/linux/if_xdp.h``. Thus, generally, the ``tx_metadata_len`` +field above should contain ``sizeof(union xsk_tx_metadata)``. + +Note that in the original implementation the ``XDP_UMEM_TX_METADATA_LEN`` +flag was not required. Applications might attempt to create a umem +with a flag first and if it fails, do another attempt without a flag.
The headroom and the metadata itself should be located right before ``xdp_desc->addr`` in the umem frame. Within a frame, the metadata diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h index d316984104107..42ec5ddaab8dc 100644 --- a/include/uapi/linux/if_xdp.h +++ b/include/uapi/linux/if_xdp.h @@ -41,6 +41,10 @@ */ #define XDP_UMEM_TX_SW_CSUM (1 << 1)
+/* Request to reserve tx_metadata_len bytes of per-chunk metadata. + */ +#define XDP_UMEM_TX_METADATA_LEN (1 << 2) + struct sockaddr_xdp { __u16 sxdp_family; __u16 sxdp_flags; diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c index caa340134b0e1..9f76ca591d54f 100644 --- a/net/xdp/xdp_umem.c +++ b/net/xdp/xdp_umem.c @@ -151,6 +151,7 @@ static int xdp_umem_account_pages(struct xdp_umem *umem) #define XDP_UMEM_FLAGS_VALID ( \ XDP_UMEM_UNALIGNED_CHUNK_FLAG | \ XDP_UMEM_TX_SW_CSUM | \ + XDP_UMEM_TX_METADATA_LEN | \ 0)
static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) @@ -204,8 +205,11 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) if (headroom >= chunk_size - XDP_PACKET_HEADROOM) return -EINVAL;
- if (mr->tx_metadata_len >= 256 || mr->tx_metadata_len % 8) - return -EINVAL; + if (mr->flags & XDP_UMEM_TX_METADATA_LEN) { + if (mr->tx_metadata_len >= 256 || mr->tx_metadata_len % 8) + return -EINVAL; + umem->tx_metadata_len = mr->tx_metadata_len; + }
umem->size = size; umem->headroom = headroom; @@ -215,7 +219,6 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) umem->pgs = NULL; umem->user = NULL; umem->flags = mr->flags; - umem->tx_metadata_len = mr->tx_metadata_len;
INIT_LIST_HEAD(&umem->xsk_dma_list); refcount_set(&umem->users, 1);