From: Albert Huang <huangjie.albert@bytedance.com> mainline inclusion from mainline-v6.7-rc1 commit 99b29a499b5fdfb7ab274835b8e4d4c11df2f6d7 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/17327 CVE: CVE-2026-74559 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- In the previous implementation, when multiple xsk sockets were associated with a single xsk_buff_pool, a situation could arise where the xsk_tx_list maintained data at the front for one xsk socket while starving the xsk sockets at the back of the list. This could result in issues such as the inability to transmit packets, increased latency, and jitter. To address this problem, we introduce a new variable called tx_budget_spent, which limits each xsk to transmit a maximum of MAX_PER_SOCKET_BUDGET tx descriptors. This allocation ensures equitable opportunities for subsequent xsk sockets to send tx descriptors. The value of MAX_PER_SOCKET_BUDGET is set to 32. Signed-off-by: Albert Huang <huangjie.albert@bytedance.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Magnus Karlsson <magnus.karlsson@intel.com> Link: https://lore.kernel.org/bpf/20231023125732.82261-1-huangjie.albert@bytedance... Conflicts: net/xdp/xsk.c include/net/xdp_sock.h [Commit 0ebc27a4c67d ("xsk: avoid data corruption on cq descriptor number") and a1356ac7749c ("xsk: Fix race condition in AF_XDP generic RX path") have been merged.] Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> --- include/net/xdp_sock.h | 7 +++++++ net/xdp/xsk.c | 18 ++++++++++++++++++ 2 files changed, 25 insertions(+) diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h index 2d3c411..4ba3294 100644 --- a/include/net/xdp_sock.h +++ b/include/net/xdp_sock.h @@ -63,6 +63,13 @@ struct xdp_sock { struct xsk_queue *tx ____cacheline_aligned_in_smp; struct list_head tx_list; + /* record the number of tx descriptors sent by this xsk and + * when it exceeds MAX_PER_SOCKET_BUDGET, an opportunity needs + * to be given to other xsks for sending tx descriptors, thereby + * preventing other XSKs from being starved. + */ + u32 tx_budget_spent; + /* Reserved for kabi consistency. */ spinlock_t rx_lock; diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index f963c30..7299542 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -33,6 +33,7 @@ #include "xsk.h" #define TX_BATCH_SIZE 32 +#define MAX_PER_SOCKET_BUDGET (TX_BATCH_SIZE) struct xsk_addrs { u32 num_descs; @@ -429,16 +430,25 @@ EXPORT_SYMBOL(xsk_tx_release); bool xsk_tx_peek_desc(struct xsk_buff_pool *pool, struct xdp_desc *desc) { + bool budget_exhausted = false; struct xdp_sock *xs; rcu_read_lock(); +again: list_for_each_entry_rcu(xs, &pool->xsk_tx_list, tx_list) { + if (xs->tx_budget_spent >= MAX_PER_SOCKET_BUDGET) { + budget_exhausted = true; + continue; + } + if (!xskq_cons_peek_desc(xs->tx, desc, pool)) { if (xskq_has_descs(xs->tx)) xskq_cons_release(xs->tx); continue; } + xs->tx_budget_spent++; + /* This is the backpressure mechanism for the Tx path. * Reserve space in the completion queue and only proceed * if there is space in it. This avoids having to implement @@ -452,6 +462,14 @@ bool xsk_tx_peek_desc(struct xsk_buff_pool *pool, struct xdp_desc *desc) return true; } + if (budget_exhausted) { + list_for_each_entry_rcu(xs, &pool->xsk_tx_list, tx_list) + xs->tx_budget_spent = 0; + + budget_exhausted = false; + goto again; + } + out: rcu_read_unlock(); return false; -- 2.9.5