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

On Thu, Feb 5, 2026 at 7:51 AM Paolo Abeni <[email protected]> wrote:
>
> On 2/5/26 12:54 PM, Simon Horman wrote:
> > This is an AI-generated review of your patch. The human sending this
> > email has considered the AI review valid, or at least plausible.
> >
> > 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.
I kind of forgot why I didn't validate it, I will decide if it should be
added after interop testing with those userland implementations.

>
> >> 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.
>
Parsing the connid from incoming packets will always check its length,
not good to move the check here then return an error for coding.

I will only leave a comment here. like:

/* Caller must ensure len does not exceed QUIC_CONN_ID_MAX_LEN. */

Thanks.