Bug 2540182 (CVE-2026-93207)

In the Linux kernel, the following vulnerability has been resolved:

SUNRPC: Zero rpc_gss_wire_cred at svcauth_gss_decode_credbody() entry

svcauth_gss_decode_credbody() writes the caller's
rpc_gss_wire_cred field by field and assigns gc_ctx.len only on
the success tail.  The caller storage is svcdata->clcred, which
lives in the per-svc_rqst gss_svc_data and is reused across
requests.  Early decode failures leave partially decoded state
mixed with residue from the prior request.

The trailing body_len tightness check is the sharpest case:
xdr_stream_decode_opaque_inline() has already written gc_ctx.data
with a borrowed inline pointer into the current request's XDR
pages, but gc_ctx.len retains its prior value.  Once the request
pages are released the pooled clcred carries a dangling pointer
paired with a stale length.

Zero the caller's rpc_gss_wire_cred at function entry so that
every early-return path leaves a deterministic all-zero cred.
On the trailing tightness-check path, gc_ctx.len is now zero
instead of stale, which neuters length-driven consumers such as
gss_svc_searchbyctx() that would otherwise walk the dangling
data pointer.