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xsk: fix NULL pointer dereference in __xsk_rcv()

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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: 804627751b ("xsk: add support for AF_XDP multi-buffer on Rx path")
Reported-by: AutonomousCodeSecurity@microsoft.com
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://patch.msgid.link/20260813215328.99311-1-blbllhy@gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Cen Zhang (Microsoft) 2026-08-13 17:53:28 -04:00 committed by Jakub Kicinski
parent 91ec203513
commit e37b2abca8
1 changed files with 27 additions and 3 deletions
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30
net/xdp/xsk.c
View File

@ -298,9 +298,11 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
u32 frame_size = __xsk_pool_get_rx_frame_size(xs->pool);
void *copy_from = xsk_copy_xdp_start(xdp), *copy_to;
u32 from_len, meta_len, rem, num_desc;
struct xdp_buff_xsk *xskb;
struct xdp_buff_xsk *xskb, *tmp;
struct xdp_buff *xsk_xdp;
LIST_HEAD(xsk_buffs);
skb_frag_t *frag;
u32 i;
from_len = xdp->data_end - copy_from;
meta_len = xdp->data - copy_from;
@ -343,23 +345,45 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
frag = &sinfo->frags[0];
}
for (i = 0; i < num_desc; i++) {
xsk_xdp = xsk_buff_alloc(xs->pool);
if (!xsk_xdp)
goto err_alloc;
xskb = container_of(xsk_xdp, struct xdp_buff_xsk, xdp);
if (unlikely(!list_empty(&xskb->list_node)))
goto err_alloc;
list_add_tail(&xskb->list_node, &xsk_buffs);
}
do {
u32 to_len = frame_size + meta_len;
u32 copied;
xsk_xdp = xsk_buff_alloc(xs->pool);
xskb = list_first_entry(&xsk_buffs, struct xdp_buff_xsk,
list_node);
list_del_init(&xskb->list_node);
xsk_xdp = &xskb->xdp;
copy_to = xsk_xdp->data - meta_len;
copied = xsk_copy_xdp(copy_to, &copy_from, to_len, &from_len, &frag, rem);
rem -= copied;
xskb = container_of(xsk_xdp, struct xdp_buff_xsk, xdp);
__xsk_rcv_zc_safe(xs, xskb, copied - meta_len,
rem ? XDP_PKT_CONTD : 0);
meta_len = 0;
} while (rem);
return 0;
err_alloc:
list_for_each_entry_safe(xskb, tmp, &xsk_buffs, list_node) {
list_del_init(&xskb->list_node);
xsk_buff_free(&xskb->xdp);
}
xs->rx_dropped++;
return -ENOMEM;
}
static bool xsk_tx_writeable(struct xdp_sock *xs)