Re: [net-next,v9,03/15] quic: provide common utilities and data structures

On 2/5/26 12:54 PM, Simon Horman wrote:
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> 
> For local reproduction steps see https://netdev-ai.bots.linux.dev/ai-local.html
> ---
> quic: provide common utilities and data structures
> 
> This patch provides foundational data structures and utilities for
> the QUIC stack, including hash tables for socket lookup, connection
> ID management, and helpers for encoding/decoding transport parameters.
> 
>> diff --git a/net/quic/common.c b/net/quic/common.c
>> new file mode 100644
>> index 000000000000..94321f3f213d
>> --- /dev/null
>> +++ b/net/quic/common.c
> 
> [ ... ]
> 
>> +/* Reads a QUIC transport parameter value. */
>> +u8 quic_get_param(u64 *pdest, u8 **pp, u32 *plen)
>> +{
>> +	u64 valuelen;
>> +
>> +	if (!quic_get_var(pp, plen, &valuelen))
>> +		return 0;
>> +
>> +	if (*plen < valuelen)
>> +		return 0;
>> +
>> +	if (!quic_get_var(pp, plen, pdest))
>> +		return 0;
>> +
>> +	return (u8)valuelen;
>> +}
> 
> Does quic_get_param() need to verify that quic_get_var() consumed exactly
> valuelen bytes?
> 
> The function reads valuelen at the first quic_get_var() call, then decodes
> the value with the second quic_get_var(). However, quic_get_var() determines
> how many bytes to consume based on the varint prefix in the data, not from
> valuelen.
> 
> If a malformed packet has valuelen=2 but the varint encoding requires 4 bytes,
> quic_get_var() will consume 4 bytes while the function returns valuelen=2.
> This could desynchronize parsing of subsequent parameters since the caller
> expects the buffer to have advanced by valuelen bytes based on the return
> value.

Hard to tell without any caller for this function. Possibly you could
drop it? IDK if enforcing such check would be correct/safe from an
interoperability PoV.

>> diff --git a/net/quic/common.h b/net/quic/common.h
>> new file mode 100644
>> index 000000000000..bfec0aaf2907
>> --- /dev/null
>> +++ b/net/quic/common.h
> 
> [ ... ]
> 
>> +#define QUIC_CONN_ID_MAX_LEN	20
> 
> [ ... ]
> 
>> +struct quic_conn_id {
>> +	u8 data[QUIC_CONN_ID_MAX_LEN];
>> +	u8 len;
>> +};
>> +
>> +static inline void quic_conn_id_update(struct quic_conn_id *conn_id, u8 *data, u32 len)
>> +{
>> +	memcpy(conn_id->data, data, len);
>> +	conn_id->len = (u8)len;
>> +}
> 
> Should quic_conn_id_update() validate that len does not exceed
> QUIC_CONN_ID_MAX_LEN before the memcpy?
> 
> The destination buffer conn_id->data is a 20-byte array, but the len
> parameter is u32 with no bounds check. If a caller passes len > 20, the
> memcpy would overflow the buffer.

It looks like the check responsibility is on the callers. I guess it
would make things more robust and simpler move the check here.

/P