Re: [PATCH net-next] net/rds: clear i_rx_lat_trace in rds_inc_path_init()

On Thu, 2026-08-13 at 12:50 +0200, Paolo Abeni wrote:
> On 8/10/26 7:56 AM, Allison Henderson wrote:
> > The commit that introduced the receive-path latency trace added the
> > clearing of inc->i_rx_lat_trace[] to rds_inc_init() only;
> > rds_inc_path_init() never got it.
> > 
> > That asymmetry matters for the one caller that reuses memory:
> > rds_tcp_data_recv() carves its rds_tcp_incoming out of a kmem_cache
> > with no zeroing and no constructor, so after rds_inc_path_init() the
> > array still holds the timestamps of whatever message previously
> > occupied that slab object.  No stale value is user-visible today -
> > every message that reaches the socket happens to overwrite all four
> > slots (RX_HDR at allocation, RX_START when the header completes,
> > RX_END at delivery, RX_CMSG at recvmsg time) before
> > RDS_CMSG_RXPATH_LATENCY reads them back as deltas - but that is a
> > property of the current writers, not of the init contract, and a
> > future trace point or an early-exit path would expose another
> > message's timestamps to userspace.
> > 
> > Clear the array in rds_inc_path_init() too, so both init helpers
> > leave the inc fully initialized.  memset is the form the clearing
> > already takes on the rds_inc_init() side since commit 1635bb548f84
> > ("net: rds: use memset to optimize the recv").  Hardening only; no
> > user-visible bug in the current code.
> > 
> > Assisted-by: Claude-Code:claude-fable-5
> > Signed-off-by: Allison Henderson <[email protected]>
> Mentioning this change in the previous series thread would have saved me
> a lot of time :(
> 
> /P
> 
Sorry about that!  You're right, the follow-up came out of the same
review pass as v2, and I should have replied to the series thread with
a pointer to it.  I'll be sure to cross-reference follow-ups like that
in the future.

Thank you for picking up all three!

Allison