[PATCH iwl-net] idpf: fix RSS LUT memcpy size

Larysa Zaremba
2026-04-29T07:42:38Z

Based on the following feedback from Sashiko (received for iXD phase 1
patchset, but valid for the net tree):

"Is the bounds check xn_params.recv_mem.iov_len < lut_buf_size sufficient?
Since lut_buf_size only represents the size of the array elements, should
this check instead verify that the payload is at least
sizeof(struct virtchnl2_rss_lut) + lut_buf_size?

[...]

Does memcpy copy the correct amount of data here? rss_lut_size stores the
number of 32-bit entries, not the size in bytes. Should it use
lut_buf_size or rss_data->rss_lut_size * sizeof(u32) instead?"

After inspecting the code, it was concluded that RSS memcpy size is in fact
4 times smaller than it has to be, since a single array entry in a u32, and
rss_data->rss_lut_size is clearly used as an array size. Required Rx buffer
size is also too small, but this is a common issue in the idpf code.

Use a full buffer size (lut_buf_size) instead of the array length
(rss_data->rss_lut_size) when doing memcpy of RSS lookup table.
While at it, increase required Rx buffer size to a whole flex-array
containing structure instead of just the array.

Link: https://sashiko.dev/#/patchset/20260323174052.5355-1-larysa.zaremba%40intel.com?part=8
Fixes: 95af467d9a4e ("idpf: configure resources for RX queues")
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
---
drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
index be66f9b2e101..a97d2e9b54d4 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
@@ -2916,7 +2916,7 @@ int idpf_send_get_set_rss_lut_msg(struct idpf_adapter *adapter,
return -EIO;

lut_buf_size = le16_to_cpu(recv_rl->lut_entries) * sizeof(u32);
- if (reply_sz < lut_buf_size)
+ if (reply_sz < lut_buf_size + sizeof(struct virtchnl2_rss_lut))
return -EIO;

/* size didn't change, we can reuse existing lut buf */
@@ -2933,7 +2933,7 @@ int idpf_send_get_set_rss_lut_msg(struct idpf_adapter *adapter,
}

do_memcpy:
- memcpy(rss_data->rss_lut, recv_rl->lut, rss_data->rss_lut_size);
+ memcpy(rss_data->rss_lut, recv_rl->lut, lut_buf_size);

return 0;
}
--
2.47.0