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bnxt: properly flush XDP redirect lists

PATCH Applied Yan Zhai 5 participants 5 messages Jun 23, 2025 – Jun 25, 2025

Subsystems (4)
Networking Network drivers BPF Broadcom bnxt_en 50 gigabit Ethernet driver
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Yan Zhai

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#0 lore raw

PATCH 1/1 bnxt: properly flush XDP redirect lists

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 7f0a168b0441 ("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 7f0a168b0441 ("bnxt_en: Add completion ring pointer in TX and RX ring structures")
Tested-by Andrew Rzeznik <[email protected]>
Signed-off-by Yan Zhai <[email protected]>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
drivers/net/ethernet/broadcom/bnxt/bnxt.c +4 -1
index 2cb3185c442c..ae89a981e052 100644
@@ -2989,6 +2989,7 @@ 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;

@@ -3042,6 +3043,8 @@ 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

@@ -3066,7 +3069,7 @@ 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;
 	}
Signature · 1 line
2.39.5
Acked-by on v1 1/1
#1 lore raw
Quoted 3 lines · Yan Zhai

We encountered following crash when testing a XDP_REDIRECT feature in production:

[...]

Quoted 11 lines

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 7f0a168b0441 ("bnxt_en: Add completion ring pointer in TX and RX ring structures") incorrectly overwrites the event mask for XDP_REDIRECT in bnxt_rx_xdp.

(To Andy + Michael:)
The initial bug was introduced in [1] commit a7559bc8c17c ("bnxt:
support transmit and free of aggregation buffers") in bnxt_rx_xdp() where case XDP_TX zeros the *event, that also carries the XDP-redirect indication.
I'm wondering if the driver should not reset the *event value? (all other drive code paths doesn't)

Quoted 5 lines

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 7f0a168b0441 ("bnxt_en: Add completion ring pointer in TX and RX ring structures")

We should also add:

Fixes a7559bc8c17c ("bnxt: support transmit and free of aggregation buffers")

[0] https://git.kernel.org/torvalds/c/7f0a168b0441 - v6.8-rc1
[1] https://git.kernel.org/torvalds/c/a7559bc8c17c - v5.19-rc1

Quoted 2 lines
Tested-by Andrew Rzeznik <[email protected]>
Signed-off-by Yan Zhai <[email protected]>
Acked-by Jesper Dangaard Brouer <[email protected]>
Quoted 34 lines
---
  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)
drivers/net/ethernet/broadcom/bnxt/bnxt.c +4 -1
index 2cb3185c442c..ae89a981e052 100644
@@ -2989,6 +2989,7 @@ 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;

@@ -3042,6 +3043,8 @@ 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

@@ -3066,7 +3069,7 @@ 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;
  	}
maintainer Reviewed-by
#2 lore raw
Quoted 7 lines · Jesper Dangaard Brouer
Quoted 3 lines · Yan Zhai

We encountered following crash when testing a XDP_REDIRECT feature in production:

[...]

Quoted 1 line
Quoted 7 lines

(To Andy + Michael:)
The initial bug was introduced in [1] commit a7559bc8c17c ("bnxt:
support transmit and free of aggregation buffers") in bnxt_rx_xdp() where case XDP_TX zeros the *event, that also carries the XDP-redirect indication.
I'm wondering if the driver should not reset the *event value? (all other drive code paths doesn't)

Resetting *event was only correct before XDP_REDIRECT support was added.

Quoted 5 lines
Quoted 5 lines

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.

Thanks for the patch. The fix is similar to edc0140cc3b7 ("bnxt_en:
Flush XDP for bnxt_poll_nitroa0()'s NAPI")

Somehow the fix was only applied to one chip's poll function and not the other chips' poll functions.

Reviewed-by Michael Chan <[email protected]>
Reviewed-by
#3 lore raw
Quoted 25 lines · Michael Chan
Quoted 7 lines · Jesper Dangaard Brouer
Quoted 3 lines · Yan Zhai

We encountered following crash when testing a XDP_REDIRECT feature in production:

[...]

Quoted 1 line
Quoted 7 lines

(To Andy + Michael:)
The initial bug was introduced in [1] commit a7559bc8c17c ("bnxt:
support transmit and free of aggregation buffers") in bnxt_rx_xdp() where case XDP_TX zeros the *event, that also carries the XDP-redirect indication.
I'm wondering if the driver should not reset the *event value? (all other drive code paths doesn't)

Resetting *event was only correct before XDP_REDIRECT support was added.

Quoted 5 lines
Quoted 5 lines

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.

Quoted 5 lines

Thanks for the patch. The fix is similar to edc0140cc3b7 ("bnxt_en:
Flush XDP for bnxt_poll_nitroa0()'s NAPI")

Somehow the fix was only applied to one chip's poll function and not the other chips' poll functions.

Odd that we missed this back then. Thanks for the fix for all other devices.

Quoted 1 line
Reviewed-by Michael Chan <[email protected]>
Reviewed-by Andy Gospodarek <[email protected]>
CI Applied
#4 lore raw
In reply to Yan Zhai
This patch was applied to netdev/net.git (main) by Jakub Kicinski <[email protected]>:

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:

Quoted 71 lines · On Mon, 23 Jun 2025 09:06:38 -0700 you wrote:

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>
Quoted 1 line

[...]

Here is the summary with links:
- [net] bnxt: properly flush XDP redirect lists

    https://git.kernel.org/netdev/net/c/9caca6ac0e26

You are awesome, thank you!

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