On Wed, Jun 11, 2025 at 02:54:09PM -0400, Chuck Lever wrote: > On 6/11/25 2:50 PM, Nikhil Jha wrote: > > On Thu, Mar 20, 2025 at 09:16:15AM -0400, Chuck Lever wrote: > >> On 3/19/25 1:02 PM, Nikhil Jha via B4 Relay wrote: > >>> When the client retransmits an operation (for example, because the > >>> server is slow to respond), a new GSS sequence number is associated with > >>> the XID. In the current kernel code the original sequence number is > >>> discarded. Subsequently, if a response to the original request is > >>> received there will be a GSS sequence number mismatch. A mismatch will > >>> trigger another retransmit, possibly repeating the cycle, and after some > >>> number of failed retries EACCES is returned. > >>> > >>> RFC2203, section 5.3.3.1 suggests a possible solution... “cache the > >>> RPCSEC_GSS sequence number of each request it sends” and "compute the > >>> checksum of each sequence number in the cache to try to match the > >>> checksum in the reply's verifier." This is what FreeBSD’s implementation > >>> does (rpc_gss_validate in sys/rpc/rpcsec_gss/rpcsec_gss.c). > >>> > >>> However, even with this cache, retransmits directly caused by a seqno > >>> mismatch can still cause a bad message interleaving that results in this > >>> bug. The RFC already suggests ignoring incorrect seqnos on the server > >>> side, and this seems symmetric, so this patchset also applies that > >>> behavior to the client. > >>> > >>> These two patches are *not* dependent on each other. I tested them by > >>> delaying packets with a Python script hooked up to NFQUEUE. If it would > >>> be helpful I can send this script along as well. > >>> > >>> Signed-off-by: Nikhil Jha <n...@janestreet.com> > >>> --- > >>> Changes since v1: > >>> * Maintain the invariant that the first seqno is always first in > >>> rq_seqnos, so that it doesn't need to be stored twice. > >>> * Minor formatting, and resending with proper mailing-list headers so the > >>> patches are easier to work with. > >>> > >>> --- > >>> Nikhil Jha (2): > >>> sunrpc: implement rfc2203 rpcsec_gss seqnum cache > >>> sunrpc: don't immediately retransmit on seqno miss > >>> > >>> include/linux/sunrpc/xprt.h | 17 +++++++++++- > >>> include/trace/events/rpcgss.h | 4 +-- > >>> include/trace/events/sunrpc.h | 2 +- > >>> net/sunrpc/auth_gss/auth_gss.c | 59 > >>> ++++++++++++++++++++++++++---------------- > >>> net/sunrpc/clnt.c | 9 +++++-- > >>> net/sunrpc/xprt.c | 3 ++- > >>> 6 files changed, 64 insertions(+), 30 deletions(-) > >>> --- > >>> base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6 > >>> change-id: 20250314-rfc2203-seqnum-cache-52389d14f567 > >>> > >>> Best regards, > >> > >> This seems like a sensible thing to do to me. > >> > >> Acked-by: Chuck Lever <chuck.le...@oracle.com> > >> > >> -- > >> Chuck Lever > > > > Hi, > > > > We've been running this patch for a while now and noticed a (very silly > > in hindsight) bug. > > > > maj_stat = gss_validate_seqno_mic(ctx, task->tk_rqstp->rq_seqnos[i], seq, > > p, len); > > > > needs to be > > > > maj_stat = gss_validate_seqno_mic(ctx, task->tk_rqstp->rq_seqnos[i++], seq, > > p, len); > > > > Or the kernel gets stuck in a loop when you have more than two retries. > > I can resend this patch but I noticed it's already made its way into > > quite a few trees. Should this be a separate patch instead? > > The course of action depends on what trees you found the patch in. > > > -- > Chuck Lever
It shows up here, so I think it's in v6.16-rc1 already. https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.16-rc1&id=08d6ee6d8a10aef958c2af16bb121070290ed589 - Nikhil
