When the kernel calls svc_reserve to downsize the expected size of an RPC reply, it fails to account for the possibility of a checksum at the end of the packet. If a client mounts a NFSv2/3 with sec=krb5i/p, and does I/O then you'll generally see messages similar to this in the server's ring buffer:
RPC request reserved 164 but used 208 While I was never able to verify it, I suspect that this problem is also the root cause of some oopses I've seen under these conditions: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=227726 This is probably also a problem for other sec= types and for NFSv4. The large reserved size for NFSv4 compound packets seems to generally paper over the problem, however. This patch adds a wrapper for svc_reserve that accounts for the possibility of a checksum. It also fixes up the appropriate callers of svc_reserve to call the wrapper. For now, it just uses a hardcoded value that I determined via testing. That value may need to be revised upward as things change, or we may want to eventually add a new auth_op that attempts to calculate this somehow. Unfortunately, there doesn't seem to be a good way to reliably determine the expected checksum length prior to actually calculating it, particularly with schemes like spkm3. Signed-off-by: Jeff Layton <[EMAIL PROTECTED]> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c index f61142a..7d47c16 100644 --- a/fs/nfsd/nfs3proc.c +++ b/fs/nfsd/nfs3proc.c @@ -175,7 +175,7 @@ nfsd3_proc_read(struct svc_rqst *rqstp, struct nfsd3_readargs *argp, if (NFSSVC_MAXBLKSIZE < resp->count) resp->count = NFSSVC_MAXBLKSIZE; - svc_reserve(rqstp, ((1 + NFS3_POST_OP_ATTR_WORDS + 3)<<2) + resp->count +4); + svc_reserve_auth(rqstp, ((1 + NFS3_POST_OP_ATTR_WORDS + 3)<<2) + resp->count +4); fh_copy(&resp->fh, &argp->fh); nfserr = nfsd_read(rqstp, &resp->fh, NULL, diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c index 4e06810..21f2ff7 100644 --- a/fs/nfsd/nfsproc.c +++ b/fs/nfsd/nfsproc.c @@ -154,7 +154,7 @@ nfsd_proc_read(struct svc_rqst *rqstp, struct nfsd_readargs *argp, argp->count); argp->count = NFSSVC_MAXBLKSIZE; } - svc_reserve(rqstp, (19<<2) + argp->count + 4); + svc_reserve_auth(rqstp, (19<<2) + argp->count + 4); resp->count = argp->count; nfserr = nfsd_read(rqstp, fh_copy(&resp->fh, &argp->fh), NULL, diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 94350f5..60f24d6 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -326,4 +326,24 @@ int svc_register(struct svc_serv *, int, unsigned short); void svc_wake_up(struct svc_serv *); void svc_reserve(struct svc_rqst *rqstp, int space); +/* + * When we want to reduce the size of the reserved space in the response + * buffer, we need to take into account the size of any checksum data that + * may be at the end of the packet. For now, just use a hardcoded value + * for each possible authflavor. This will need to be updated when new + * encryption types or algorithms are added, or we'll have to come up with + * a way to reasonably calculate this on the fly (maybe via a new auth_op). + */ +static inline void +svc_reserve_auth(struct svc_rqst *rqstp, int space) +{ + int added_space = 0; + + switch(rqstp->rq_authop->flavour) { + case RPC_AUTH_GSS: + added_space = 56; /* determined empirically */ + } + return svc_reserve(rqstp, space + added_space); +} + #endif /* SUNRPC_SVC_H */ diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c index 0aab5b5..2d390d1 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -379,7 +379,7 @@ svc_process(struct svc_serv *serv, struct svc_rqst *rqstp) * better idea of reply size */ if (procp->pc_xdrressize) - svc_reserve(rqstp, procp->pc_xdrressize<<2); + svc_reserve_auth(rqstp, procp->pc_xdrressize<<2); /* Call the function that processes the request. */ if (!versp->vs_dispatch) { diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
