The nest attribute NBD_ATTR_DEVICE_LIST was not accounted for when allocating the message, resulting in -EMSGSIZE. As __alloc_skb aligns size requests to SMP_CACHE_BYTES and SLUB will end up allocating more than requested, this can hardly be reproduced on most setups. However, I managed to test this on a 32-bit x86 with 15 entries, by loading with nbds_max=15. It failed with -EMSGSIZE, while it worked with 14 or 16 entries. Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx> --- drivers/block/nbd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 43cff01a5a67..19551d8ca355 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -2265,6 +2265,7 @@ static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info) msg_size = nla_total_size(nla_attr_size(sizeof(u32)) + nla_attr_size(sizeof(u8))); msg_size *= (index == -1) ? nbd_total_devices : 1; + msg_size += nla_total_size(0); /* for NBD_ATTR_DEVICE_LIST */ reply = genlmsg_new(msg_size, GFP_KERNEL); if (!reply) -- 2.25.1
