Re: [PATCH net v4] xsk: fix NULL pointer dereference in __xsk_rcv()
Simon Horman <[email protected]>
| Newsgroups | org.kernel.vger.bpf,org.kernel.vger.linux-kernel,org.kernel.vger.netdev |
|---|---|
| Message-ID | <[email protected]> |
On Thu, Aug 13, 2026 at 05:53:28PM -0400, Cen Zhang (Microsoft) wrote:
> In the __xsk_rcv() multi-buffer path, xsk_buff_alloc() is called in a
> loop without checking its return value. xsk_buff_can_alloc() only
> counts fill queue entries without validating their addresses, so it
> can succeed while xsk_buff_alloc() rejects all remaining entries and
> returns NULL.
>
> Oops: general protection fault, probably for non-canonical address
> 0xdffffc0000000000
> KASAN: null-ptr-deref in range
> [0x0000000000000000-0x0000000000000007]
> RIP: 0010:__xsk_rcv+0x426/0xc20 (net/xdp/xsk.c:350)
> Call Trace:
> xsk_generic_rcv+0x26d/0x5f0
> xdp_do_generic_redirect+0x3c5/0xcf0
> do_xdp_generic+0x92f/0xe70
> __netif_receive_skb_core.constprop.0+0xf7e/0x2b30
>
> Fix this with a two-stage transaction. First allocate and stage all
> buffers required for the packet, recycling all staged buffers with
> xsk_buff_free() if any allocation fails. Only after this stage
> succeeds, copy the data, reserve the RX descriptors, and release the
> buffers in an error-free loop.
>
> Fixes: 804627751b42 ("xsk: add support for AF_XDP multi-buffer on Rx path")
> Reported-by: [email protected]
> Signed-off-by: Cen Zhang (Microsoft) <[email protected]>
Reviewed-by: Simon Horman <[email protected]>