6.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Fernando Fernandez Mancera fmancera@suse.de
[ Upstream commit 0ebc27a4c67d44e5ce88d21cdad8201862b78837 ]
Since commit 30f241fcf52a ("xsk: Fix immature cq descriptor production"), the descriptor number is stored in skb control block and xsk_cq_submit_addr_locked() relies on it to put the umem addrs onto pool's completion queue.
skb control block shouldn't be used for this purpose as after transmit xsk doesn't have control over it and other subsystems could use it. This leads to the following kernel panic due to a NULL pointer dereference.
BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 2 UID: 1 PID: 927 Comm: p4xsk.bin Not tainted 6.16.12+deb14-cloud-amd64 #1 PREEMPT(lazy) Debian 6.16.12-1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 RIP: 0010:xsk_destruct_skb+0xd0/0x180 [...] Call Trace: <IRQ> ? napi_complete_done+0x7a/0x1a0 ip_rcv_core+0x1bb/0x340 ip_rcv+0x30/0x1f0 __netif_receive_skb_one_core+0x85/0xa0 process_backlog+0x87/0x130 __napi_poll+0x28/0x180 net_rx_action+0x339/0x420 handle_softirqs+0xdc/0x320 ? handle_edge_irq+0x90/0x1e0 do_softirq.part.0+0x3b/0x60 </IRQ> <TASK> __local_bh_enable_ip+0x60/0x70 __dev_direct_xmit+0x14e/0x1f0 __xsk_generic_xmit+0x482/0xb70 ? __remove_hrtimer+0x41/0xa0 ? __xsk_generic_xmit+0x51/0xb70 ? _raw_spin_unlock_irqrestore+0xe/0x40 xsk_sendmsg+0xda/0x1c0 __sys_sendto+0x1ee/0x200 __x64_sys_sendto+0x24/0x30 do_syscall_64+0x84/0x2f0 ? __pfx_pollwake+0x10/0x10 ? __rseq_handle_notify_resume+0xad/0x4c0 ? restore_fpregs_from_fpstate+0x3c/0x90 ? switch_fpu_return+0x5b/0xe0 ? do_syscall_64+0x204/0x2f0 ? do_syscall_64+0x204/0x2f0 ? do_syscall_64+0x204/0x2f0 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK> [...] Kernel panic - not syncing: Fatal exception in interrupt Kernel Offset: 0x1c000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
Instead use the skb destructor_arg pointer along with pointer tagging. As pointers are always aligned to 8B, use the bottom bit to indicate whether this a single address or an allocated struct containing several addresses.
Fixes: 30f241fcf52a ("xsk: Fix immature cq descriptor production") Closes: https://lore.kernel.org/netdev/0435b904-f44f-48f8-afb0-68868474bf1c@nop.hu/ Suggested-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Fernando Fernandez Mancera fmancera@suse.de Reviewed-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Reviewed-by: Jason Xing kerneljasonxing@gmail.com Link: https://patch.msgid.link/20251124171409.3845-1-fmancera@suse.de Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/xdp/xsk.c | 143 +++++++++++++++++++++++++++++++------------------- 1 file changed, 88 insertions(+), 55 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 01f258894faeb..78fc25e88d7c3 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -36,20 +36,13 @@ #define TX_BATCH_SIZE 32 #define MAX_PER_SOCKET_BUDGET 32
-struct xsk_addr_node { - u64 addr; - struct list_head addr_node; -}; - -struct xsk_addr_head { +struct xsk_addrs { u32 num_descs; - struct list_head addrs_list; + u64 addrs[MAX_SKB_FRAGS + 1]; };
static struct kmem_cache *xsk_tx_generic_cache;
-#define XSKCB(skb) ((struct xsk_addr_head *)((skb)->cb)) - void xsk_set_rx_need_wakeup(struct xsk_buff_pool *pool) { if (pool->cached_need_wakeup & XDP_WAKEUP_RX) @@ -558,29 +551,68 @@ static int xsk_cq_reserve_locked(struct xsk_buff_pool *pool) return ret; }
+static bool xsk_skb_destructor_is_addr(struct sk_buff *skb) +{ + return (uintptr_t)skb_shinfo(skb)->destructor_arg & 0x1UL; +} + +static u64 xsk_skb_destructor_get_addr(struct sk_buff *skb) +{ + return (u64)((uintptr_t)skb_shinfo(skb)->destructor_arg & ~0x1UL); +} + +static void xsk_skb_destructor_set_addr(struct sk_buff *skb, u64 addr) +{ + skb_shinfo(skb)->destructor_arg = (void *)((uintptr_t)addr | 0x1UL); +} + +static void xsk_inc_num_desc(struct sk_buff *skb) +{ + struct xsk_addrs *xsk_addr; + + if (!xsk_skb_destructor_is_addr(skb)) { + xsk_addr = (struct xsk_addrs *)skb_shinfo(skb)->destructor_arg; + xsk_addr->num_descs++; + } +} + +static u32 xsk_get_num_desc(struct sk_buff *skb) +{ + struct xsk_addrs *xsk_addr; + + if (xsk_skb_destructor_is_addr(skb)) + return 1; + + xsk_addr = (struct xsk_addrs *)skb_shinfo(skb)->destructor_arg; + + return xsk_addr->num_descs; +} + static void xsk_cq_submit_addr_locked(struct xsk_buff_pool *pool, struct sk_buff *skb) { - struct xsk_addr_node *pos, *tmp; + u32 num_descs = xsk_get_num_desc(skb); + struct xsk_addrs *xsk_addr; u32 descs_processed = 0; unsigned long flags; - u32 idx; + u32 idx, i;
spin_lock_irqsave(&pool->cq_lock, flags); idx = xskq_get_prod(pool->cq);
- xskq_prod_write_addr(pool->cq, idx, - (u64)(uintptr_t)skb_shinfo(skb)->destructor_arg); - descs_processed++; + if (unlikely(num_descs > 1)) { + xsk_addr = (struct xsk_addrs *)skb_shinfo(skb)->destructor_arg;
- if (unlikely(XSKCB(skb)->num_descs > 1)) { - list_for_each_entry_safe(pos, tmp, &XSKCB(skb)->addrs_list, addr_node) { + for (i = 0; i < num_descs; i++) { xskq_prod_write_addr(pool->cq, idx + descs_processed, - pos->addr); + xsk_addr->addrs[i]); descs_processed++; - list_del(&pos->addr_node); - kmem_cache_free(xsk_tx_generic_cache, pos); } + kmem_cache_free(xsk_tx_generic_cache, xsk_addr); + } else { + xskq_prod_write_addr(pool->cq, idx, + xsk_skb_destructor_get_addr(skb)); + descs_processed++; } xskq_prod_submit_n(pool->cq, descs_processed); spin_unlock_irqrestore(&pool->cq_lock, flags); @@ -595,16 +627,6 @@ static void xsk_cq_cancel_locked(struct xsk_buff_pool *pool, u32 n) spin_unlock_irqrestore(&pool->cq_lock, flags); }
-static void xsk_inc_num_desc(struct sk_buff *skb) -{ - XSKCB(skb)->num_descs++; -} - -static u32 xsk_get_num_desc(struct sk_buff *skb) -{ - return XSKCB(skb)->num_descs; -} - static void xsk_destruct_skb(struct sk_buff *skb) { struct xsk_tx_metadata_compl *compl = &skb_shinfo(skb)->xsk_meta; @@ -621,27 +643,22 @@ static void xsk_destruct_skb(struct sk_buff *skb) static void xsk_skb_init_misc(struct sk_buff *skb, struct xdp_sock *xs, u64 addr) { - BUILD_BUG_ON(sizeof(struct xsk_addr_head) > sizeof(skb->cb)); - INIT_LIST_HEAD(&XSKCB(skb)->addrs_list); skb->dev = xs->dev; skb->priority = READ_ONCE(xs->sk.sk_priority); skb->mark = READ_ONCE(xs->sk.sk_mark); - XSKCB(skb)->num_descs = 0; skb->destructor = xsk_destruct_skb; - skb_shinfo(skb)->destructor_arg = (void *)(uintptr_t)addr; + xsk_skb_destructor_set_addr(skb, addr); }
static void xsk_consume_skb(struct sk_buff *skb) { struct xdp_sock *xs = xdp_sk(skb->sk); u32 num_descs = xsk_get_num_desc(skb); - struct xsk_addr_node *pos, *tmp; + struct xsk_addrs *xsk_addr;
if (unlikely(num_descs > 1)) { - list_for_each_entry_safe(pos, tmp, &XSKCB(skb)->addrs_list, addr_node) { - list_del(&pos->addr_node); - kmem_cache_free(xsk_tx_generic_cache, pos); - } + xsk_addr = (struct xsk_addrs *)skb_shinfo(skb)->destructor_arg; + kmem_cache_free(xsk_tx_generic_cache, xsk_addr); }
skb->destructor = sock_wfree; @@ -662,7 +679,6 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, { struct xsk_buff_pool *pool = xs->pool; u32 hr, len, ts, offset, copy, copied; - struct xsk_addr_node *xsk_addr; struct sk_buff *skb = xs->skb; struct page *page; void *buffer; @@ -680,16 +696,26 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
xsk_skb_init_misc(skb, xs, desc->addr); } else { - xsk_addr = kmem_cache_zalloc(xsk_tx_generic_cache, GFP_KERNEL); - if (!xsk_addr) - return ERR_PTR(-ENOMEM); + struct xsk_addrs *xsk_addr; + + if (xsk_skb_destructor_is_addr(skb)) { + xsk_addr = kmem_cache_zalloc(xsk_tx_generic_cache, + GFP_KERNEL); + if (!xsk_addr) + return ERR_PTR(-ENOMEM); + + xsk_addr->num_descs = 1; + xsk_addr->addrs[0] = xsk_skb_destructor_get_addr(skb); + skb_shinfo(skb)->destructor_arg = (void *)xsk_addr; + } else { + xsk_addr = (struct xsk_addrs *)skb_shinfo(skb)->destructor_arg; + }
/* in case of -EOVERFLOW that could happen below, * xsk_consume_skb() will release this node as whole skb * would be dropped, which implies freeing all list elements */ - xsk_addr->addr = desc->addr; - list_add_tail(&xsk_addr->addr_node, &XSKCB(skb)->addrs_list); + xsk_addr->addrs[xsk_addr->num_descs] = desc->addr; }
addr = desc->addr; @@ -765,10 +791,25 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, xsk_skb_init_misc(skb, xs, desc->addr); } else { int nr_frags = skb_shinfo(skb)->nr_frags; - struct xsk_addr_node *xsk_addr; + struct xsk_addrs *xsk_addr; struct page *page; u8 *vaddr;
+ if (xsk_skb_destructor_is_addr(skb)) { + xsk_addr = kmem_cache_zalloc(xsk_tx_generic_cache, + GFP_KERNEL); + if (!xsk_addr) { + err = -ENOMEM; + goto free_err; + } + + xsk_addr->num_descs = 1; + xsk_addr->addrs[0] = xsk_skb_destructor_get_addr(skb); + skb_shinfo(skb)->destructor_arg = (void *)xsk_addr; + } else { + xsk_addr = (struct xsk_addrs *)skb_shinfo(skb)->destructor_arg; + } + if (unlikely(nr_frags == (MAX_SKB_FRAGS - 1) && xp_mb_desc(desc))) { err = -EOVERFLOW; goto free_err; @@ -780,13 +821,6 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, goto free_err; }
- xsk_addr = kmem_cache_zalloc(xsk_tx_generic_cache, GFP_KERNEL); - if (!xsk_addr) { - __free_page(page); - err = -ENOMEM; - goto free_err; - } - vaddr = kmap_local_page(page); memcpy(vaddr, buffer, len); kunmap_local(vaddr); @@ -794,8 +828,7 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, skb_add_rx_frag(skb, nr_frags, page, 0, len, PAGE_SIZE); refcount_add(PAGE_SIZE, &xs->sk.sk_wmem_alloc);
- xsk_addr->addr = desc->addr; - list_add_tail(&xsk_addr->addr_node, &XSKCB(skb)->addrs_list); + xsk_addr->addrs[xsk_addr->num_descs] = desc->addr; }
if (first_frag && desc->options & XDP_TX_METADATA) { @@ -1892,7 +1925,7 @@ static int __init xsk_init(void) goto out_pernet;
xsk_tx_generic_cache = kmem_cache_create("xsk_generic_xmit_cache", - sizeof(struct xsk_addr_node), + sizeof(struct xsk_addrs), 0, SLAB_HWCACHE_ALIGN, NULL); if (!xsk_tx_generic_cache) { err = -ENOMEM;