bnxt: properly flush XDP redirect lists

Yan Zhai · smb49 · commit 03710df955e3 · 2025-09-16T14:51:54.000+02:00
BugLink: https://bugs.launchpad.net/bugs/2121266 [ Upstream commit 9caca6ac0e26cd20efd490d8b3b2ffb1c7c00f6f ] We encountered following crash when testing a XDP_REDIRECT feature in production: [56251.579676] list_add corruption. next->prev should be prev (ffff93120dd40f30), but was ffffb301ef3a6740. (next=ffff93120dd 40f30). [56251.601413] ------------[ cut here ]------------ [56251.611357] kernel BUG at lib/list_debug.c:29! [56251.621082] Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [56251.632073] CPU: 111 UID: 0 PID: 0 Comm: swapper/111 Kdump: loaded Tainted: P O 6.12.33-cloudflare-2025.6. 3 #1 [56251.653155] Tainted: [P]=PROPRIETARY_MODULE, [O]=OOT_MODULE [56251.663877] Hardware name: MiTAC GC68B-B8032-G11P6-GPU/S8032GM-HE-CFR, BIOS V7.020.B10-sig 01/22/2025 [56251.682626] RIP: 0010:__list_add_valid_or_report+0x4b/0xa0 [56251.693203] Code: 0e 48 c7 c7 68 e7 d9 97 e8 42 16 fe ff 0f 0b 48 8b 52 08 48 39 c2 74 14 48 89 f1 48 c7 c7 90 e7 d9 97 48 89 c6 e8 25 16 fe ff <0f> 0b 4c 8b 02 49 39 f0 74 14 48 89 d1 48 c7 c7 e8 e7 d9 97 4c 89 [56251.725811] RSP: 0018:ffff93120dd40b80 EFLAGS: 00010246 [56251.736094] RAX: 0000000000000075 RBX: ffffb301e6bba9d8 RCX: 0000000000000000 [56251.748260] RDX: 0000000000000000 RSI: ffff9149afda0b80 RDI: ffff9149afda0b80 [56251.760349] RBP: ffff9131e49c8000 R08: 0000000000000000 R09: ffff93120dd40a18 [56251.772382] R10: ffff9159cf2ce1a8 R11: 0000000000000003 R12: ffff911a80850000 [56251.784364] R13: ffff93120fbc7000 R14: 0000000000000010 R15: ffff9139e7510e40 [56251.796278] FS: 0000000000000000(0000) GS:ffff9149afd80000(0000) knlGS:0000000000000000 [56251.809133] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [56251.819561] CR2: 00007f5e85e6f300 CR3: 00000038b85e2006 CR4: 0000000000770ef0 [56251.831365] PKRU: 55555554 [56251.838653] Call Trace: [56251.845560] <IRQ> [56251.851943] cpu_map_enqueue.cold+0x5/0xa [56251.860243] xdp_do_redirect+0x2d9/0x480 [56251.868388] bnxt_rx_xdp+0x1d8/0x4c0 [bnxt_en] [56251.877028] bnxt_rx_pkt+0x5f7/0x19b0 [bnxt_en] [56251.885665] ? cpu_max_write+0x1e/0x100 [56251.893510] ? srso_alias_return_thunk+0x5/0xfbef5 [56251.902276] __bnxt_poll_work+0x190/0x340 [bnxt_en] [56251.911058] bnxt_poll+0xab/0x1b0 [bnxt_en] [56251.919041] ? srso_alias_return_thunk+0x5/0xfbef5 [56251.927568] ? srso_alias_return_thunk+0x5/0xfbef5 [56251.935958] ? srso_alias_return_thunk+0x5/0xfbef5 [56251.944250] __napi_poll+0x2b/0x160 [56251.951155] bpf_trampoline_6442548651+0x79/0x123 [56251.959262] __napi_poll+0x5/0x160 [56251.966037] net_rx_action+0x3d2/0x880 [56251.973133] ? srso_alias_return_thunk+0x5/0xfbef5 [56251.981265] ? srso_alias_return_thunk+0x5/0xfbef5 [56251.989262] ? __hrtimer_run_queues+0x162/0x2a0 [56251.996967] ? srso_alias_return_thunk+0x5/0xfbef5 [56252.004875] ? srso_alias_return_thunk+0x5/0xfbef5 [56252.012673] ? bnxt_msix+0x62/0x70 [bnxt_en] [56252.019903] handle_softirqs+0xcf/0x270 [56252.026650] irq_exit_rcu+0x67/0x90 [56252.032933] common_interrupt+0x85/0xa0 [56252.039498] </IRQ> [56252.044246] <TASK> [56252.048935] asm_common_interrupt+0x26/0x40 [56252.055727] RIP: 0010:cpuidle_enter_state+0xb8/0x420 [56252.063305] Code: dc 01 00 00 e8 f9 79 3b ff e8 64 f7 ff ff 49 89 c5 0f 1f 44 00 00 31 ff e8 a5 32 3a ff 45 84 ff 0f 85 ae 01 00 00 fb 45 85 f6 <0f> 88 88 01 00 00 48 8b 04 24 49 63 ce 4c 89 ea 48 6b f1 68 48 29 [56252.088911] RSP: 0018:ffff93120c97fe98 EFLAGS: 00000202 [56252.096912] RAX: ffff9149afd80000 RBX: ffff9141d3a72800 RCX: 0000000000000000 [56252.106844] RDX: 00003329176c6b98 RSI: ffffffe36db3fdc7 RDI: 0000000000000000 [56252.116733] RBP: 0000000000000002 R08: 0000000000000002 R09: 000000000000004e [56252.126652] R10: ffff9149afdb30c4 R11: 071c71c71c71c71c R12: ffffffff985ff860 [56252.136637] R13: 00003329176c6b98 R14: 0000000000000002 R15: 0000000000000000 [56252.146667] ? cpuidle_enter_state+0xab/0x420 [56252.153909] cpuidle_enter+0x2d/0x40 [56252.160360] do_idle+0x176/0x1c0 [56252.166456] cpu_startup_entry+0x29/0x30 [56252.173248] start_secondary+0xf7/0x100 [56252.179941] common_startup_64+0x13e/0x141 [56252.186886] </TASK> From the crash dump, we found that the cpu_map_flush_list inside redirect info is partially corrupted: its list_head->next points to itself, but list_head->prev points to a valid list of unflushed bq entries. This turned out to be a result of missed XDP flush on redirect lists. By digging in the actual source code, we found that commit 7f0a168 ("bnxt_en: Add completion ring pointer in TX and RX ring structures") incorrectly overwrites the event mask for XDP_REDIRECT in bnxt_rx_xdp. We can stably reproduce this crash by returning XDP_TX and XDP_REDIRECT randomly for incoming packets in a naive XDP program. Properly propagate the XDP_REDIRECT events back fixes the crash. Fixes: a7559bc ("bnxt: support transmit and free of aggregation buffers") Tested-by: Andrew Rzeznik <arzeznik@cloudflare.com> Signed-off-by: Yan Zhai <yan@cloudflare.com> Acked-by: Jesper Dangaard Brouer <hawk@kernel.org> Reviewed-by: Michael Chan <michael.chan@broadcom.com> Reviewed-by: Andy Gospodarek <gospo@broadcom.com> Link: https://patch.msgid.link/aFl7jpCNzscumuN2@debian.debian Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Noah Wager <noah.wager@canonical.com> Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -2954,6 +2954,7 @@ static int __bnxt_poll_work(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
 {
 	struct bnxt_napi *bnapi = cpr->bnapi;
 	u32 raw_cons = cpr->cp_raw_cons;
+	bool flush_xdp = false;
 	u32 cons;
 	int rx_pkts = 0;
 	u8 event = 0;
@@ -3007,6 +3008,8 @@ static int __bnxt_poll_work(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
 			else
 				rc = bnxt_force_rx_discard(bp, cpr, &raw_cons,
 							   &event);
+			if (event & BNXT_REDIRECT_EVENT)
+				flush_xdp = true;
 			if (likely(rc >= 0))
 				rx_pkts += rc;
 			/* Increment rx_pkts when rc is -ENOMEM to count towards
@@ -3031,7 +3034,7 @@ static int __bnxt_poll_work(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
 		}
 	}
 
-	if (event & BNXT_REDIRECT_EVENT) {
+	if (flush_xdp) {
 		xdp_do_flush();
 		event &= ~BNXT_REDIRECT_EVENT;
 	}

Original file line number	Diff line number	Diff line change
`@@ -2954,6 +2954,7 @@ static int __bnxt_poll_work(struct bnxt bp, struct bnxt_cp_ring_info cpr,`
`2954`	`2954`	`{`
`2955`	`2955`	`struct bnxt_napi *bnapi = cpr->bnapi;`
`2956`	`2956`	`u32 raw_cons = cpr->cp_raw_cons;`
	`2957`	`+ bool flush_xdp = false;`
`2957`	`2958`	`u32 cons;`
`2958`	`2959`	`int rx_pkts = 0;`
`2959`	`2960`	`u8 event = 0;`
`@@ -3007,6 +3008,8 @@ static int __bnxt_poll_work(struct bnxt bp, struct bnxt_cp_ring_info cpr,`
`3007`	`3008`	`else`
`3008`	`3009`	`rc = bnxt_force_rx_discard(bp, cpr, &raw_cons,`
`3009`	`3010`	`&event);`
	`3011`	`+ if (event & BNXT_REDIRECT_EVENT)`
	`3012`	`+ flush_xdp = true;`
`3010`	`3013`	`if (likely(rc >= 0))`
`3011`	`3014`	`rx_pkts += rc;`
`3012`	`3015`	`/* Increment rx_pkts when rc is -ENOMEM to count towards`
`@@ -3031,7 +3034,7 @@ static int __bnxt_poll_work(struct bnxt bp, struct bnxt_cp_ring_info cpr,`
`3031`	`3034`	`}`
`3032`	`3035`	`}`
`3033`	`3036`
`3034`		`- if (event & BNXT_REDIRECT_EVENT) {`
	`3037`	`+ if (flush_xdp) {`
`3035`	`3038`	`xdp_do_flush();`
`3036`	`3039`	`event &= ~BNXT_REDIRECT_EVENT;`
`3037`	`3040`	`}`