In the Linux kernel, the following vulnerability has been resolved: xsk: fix NULL pointer dereference in __xsk_rcv() In the __xsk_rcv() mu

In the Linux kernel, the following vulnerability has been resolved:

xsk: fix NULL pointer dereference in __xsk_rcv()

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.