From 2e4ce62385c1b8a887c5370af058ac7b52a8eaf9 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Thu, 28 May 2026 15:32:10 -0400 Subject: [PATCH] SUNRPC: reject duplicate CREDS_VALUE options gssx_dec_option_array() walks the wire-supplied option array and, for every entry whose name matches CREDS_VALUE, calls gssx_dec_linux_creds() on the same struct svc_cred. That helper unconditionally installs a fresh groups_alloc() result into creds->cr_group_info without releasing whatever pointer was already there: for (i = 0; i < count; i++) { ... decode name ... if (length == sizeof(CREDS_VALUE) && memcmp(p, CREDS_VALUE, sizeof(CREDS_VALUE)) == 0) { err = gssx_dec_linux_creds(xdr, creds); ... } } A reply that carries two CREDS_VALUE entries therefore overwrites cr_group_info on the second iteration and orphans the group_info allocated by the first call. The earlier free_creds path only releases the last cr_group_info via free_svc_cred(), so the first allocation's refcount stays at one and its kvmalloc-backed storage is leaked. No in-tree caller of gssp_accept_sec_context_upcall() expects more than one CREDS_VALUE per reply. Fix by tracking whether a CREDS_VALUE option has already been decoded and returning -EINVAL on any subsequent match, so the free_creds path releases the single group_info that was installed. Fixes: 1d658336b05f ("SUNRPC: Add RPC based upcall mechanism for RPCGSS auth") Cc: stable@vger.kernel.org Assisted-by: kres (claude-opus-4-7) Signed-off-by: Chris Mason Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260528-tier2-v1-3-d026a1415e0b@oracle.com Signed-off-by: Chuck Lever --- net/sunrpc/auth_gss/gss_rpc_xdr.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/sunrpc/auth_gss/gss_rpc_xdr.c b/net/sunrpc/auth_gss/gss_rpc_xdr.c index f2b8f919adea..0549edae1ebe 100644 --- a/net/sunrpc/auth_gss/gss_rpc_xdr.c +++ b/net/sunrpc/auth_gss/gss_rpc_xdr.c @@ -231,6 +231,7 @@ static int gssx_dec_option_array(struct xdr_stream *xdr, struct gssx_option_array *oa) { struct svc_cred *creds; + bool creds_decoded = false; u32 count, i; __be32 *p; int err; @@ -281,9 +282,14 @@ static int gssx_dec_option_array(struct xdr_stream *xdr, if (length == sizeof(CREDS_VALUE) && memcmp(p, CREDS_VALUE, sizeof(CREDS_VALUE)) == 0) { /* We have creds here. parse them */ + if (creds_decoded) { + err = -EINVAL; + goto free_creds; + } err = gssx_dec_linux_creds(xdr, creds); if (err) goto free_creds; + creds_decoded = true; oa->data[0].value.len = 1; /* presence */ } else { /* consume uninteresting buffer */