Re: [PATCH net v4] bnxt_en: Bound SW TPA IDs to prevent crashes

[Paolo Abeni]

On 8/28/26 9:08 PM, Joe Damato wrote:
> TPA IDs are generated by FW and can be up to 1024. bnxt_alloc_agg_idx is
> intended to wrap the FW ID down to a software ID which is used to index
> rxr->rx_tpa, and to generate a mapping between FW IDs and the wrapped
> software ID.
> 
> On a 57608 with firmware version 233, the firmware advertises 32
> concurrent TPAs. As of the commit under fixes, bp->max_tpa on this NIC
> is set to 32.
> 
> If the software ID from bnxt_alloc_agg_idx is above 31, this results in
> an invalid address being loaded on this line:
> 
>   tpa_info = &rxr->rx_tpa[agg_id];
> 
> because rx_tpa is allocated with only bp->max_tpa (32) entries. Writes
> to tpa_info later in the code are out of bounds.
> 
> This bug results in a crash at boot:
> 
> Oops: general protection fault, kernel NULL pointer dereference 0x8: 0000 [#1] SMP NOPTI
> RIP: 0010:bnxt_rx_pkt+0xc0/0x1560
> RSP: 0018:ffffc900009b8c78 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000048 RCX: 0000000206682516
> RDX: ffffc900009b8db4 RSI: 0000000000000000 RDI: 01ffffff038fe1c0
> RBP: ffffc9006e687480 R08: ffffc9006e687000 R09: 0000000000003048
> R10: 0000000000000480 R11: ffff8881c6083900 R12: 0000000006682516
> R13: ffff8881c6095400 R14: 0000000000000016 R15: ffff8881c6b66680
> FS:  0000000000000000(0000) GS:ffff88fef3c77000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fc8bda40584 CR3: 000000807c812001 CR4: 0000000008772ef0
> PKRU: 55555554
> Call Trace:
>  <IRQ>
>  ? __netif_receive_skb_list_core+0x1ca/0x250
>  __bnxt_poll_work+0x152/0x280
>  bnxt_poll_p5+0x1cd/0x480
>  __napi_poll+0x30/0x180
>  net_rx_action+0x20b/0x3b0
>  ? note_gp_changes+0x53/0xe0
>  ? tick_setup_sched_timer+0x180/0x180
>  ? __napi_schedule+0x9a/0xb0
>  ? bnxt_msix+0x24/0x30
>  handle_softirqs+0xdd/0x2c0
>  __irq_exit_rcu.llvm.3171231171502365008+0x47/0xf0
>  common_interrupt+0x85/0x90
>  </IRQ>
>  <TASK>
>  asm_common_interrupt+0x22/0x40
> 
> This stack trace is from a crash triggered when an out of bounds rx_tpa
> is dereferenced. The invalid write mentioned above is silent in this
> particular crash.
> 
> Fix this by allocating rx_tpa with bp->max_tpa rounded up to the next
> power of 2 (bp->max_tpa_roundup_size) entries and masking the FW TPA ID
> with that size, so the wrapped ID can never index past the end of the
> array.
> 
> Fixes: 54c28fab2fa5 ("bnxt_en: Set bp->max_tpa according to what the FW supports")
> Reported-by: Raphael Cardoso Fernandes <raphaelcf@xxxxxxxx>
> Suggested-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Joe Damato <joe@xxxxxxx>
> ---
> v4:
>   - Moved bp->max_tpa_roundup_size init out of the early return path and
>     documented that TPA is unsupported there, as suggested by Michael.

Clashiko quite convincingly elaborates that the above is not enough:

https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260828190900.1767611-1-joe%40dama.to

Could you please have a look?

/P