netdev - Re: [PATCH net v4] xsk: avoid data corruption on cq descriptor number

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAL+tcoCGP8crix=NWca9PBMF4z9NAXKJu8kyTdKanb3n7JEpWQ@mail.gmail.com>
Date: Wed, 19 Nov 2025 07:57:41 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Fernando Fernandez Mancera <fmancera@...e.de>
Cc: netdev@...r.kernel.org, csmate@....hu, maciej.fijalkowski@...el.com, 
	bpf@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org
Subject: Re: [PATCH net v4] xsk: avoid data corruption on cq descriptor number

On Tue, Nov 18, 2025 at 8:48 PM Fernando Fernandez Mancera
<fmancera@...e.de> wrote:
>
> 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@...nel.org>
> Signed-off-by: Fernando Fernandez Mancera <fmancera@...e.de>

Reviewed-by: Jason Xing <kerneljasonxing@...il.com>

Thanks for your effort and the fix!