Hi Paolo, On 21/12/2024 09:51, Paolo Abeni wrote: > Syzbot reported the following splat: (...) > Eric noted a probable shinfo->nr_frags corruption, which indeed > occurs. > > The root cause is a buggy MPTCP option len computation in some > circumstances: the ADD_ADDR option should be mutually exclusive > with DSS since the blamed commit. > > Still, mptcp_established_options_add_addr() tries to set the > relevant info in mptcp_out_options, if the remaining space is > large enough even when DSS is present. > > Since the ADD_ADDR infos and the DSS share the same union > fields, adding first corrupts the latter. In the worst-case > scenario, such corruption increases the DSS binary layout, > exceeding the computed length and possibly overwriting the > skb shared info. > > Address the issue by enforcing mutual exclusion in > mptcp_established_options_add_addr(), too. Thank you for the investigation and the fix, it looks good to me: Reviewed-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx> > Reported-by: syzbot+38a095a81f30d82884c1@xxxxxxxxxxxxxxxxxxxxxxxxx If you don't mind, can you please add these two tags when applying the patches to help to track the backports? Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/538 Cc: stable@xxxxxxxxxxxxxxx > Fixes: 1bff1e43a30e ("mptcp: optimize out option generation") > Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx> Cheers, Matt -- Sponsored by the NGI0 Core fund.
