selinux: fix selinux_xfrm_alloc_user() to set correct ctx_len

commit 86c8db86af43f52f682e53a0f2f0828683be1e52 upstream.

We should count the terminating NUL byte as part of the ctx_len.
Otherwise, UBSAN logs a warning:
  UBSAN: array-index-out-of-bounds in security/selinux/xfrm.c:99:14
  index 60 is out of range for type 'char [*]'

The allocation itself is correct so there is no actual out of bounds
indexing, just a warning.

Cc: stable@vger.kernel.org
Suggested-by: Christian Göttsche <cgzones@googlemail.com>
Link: https://lore.kernel.org/selinux/CAEjxPJ6tA5+LxsGfOJokzdPeRomBHjKLBVR6zbrg+_w3ZZbM3A@mail.gmail.com/
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/selinux/xfrm.c b/security/selinux/xfrm.c
index debe15207d2bfab57a3d10802ae6e031069980cf..6809332ab20300d0ad1abf8e5a7cca8e1bc00e24 100644 (file)
--- a/security/selinux/xfrm.c
+++ b/security/selinux/xfrm.c
@@ -95,7 +95,7 @@ static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
 
        ctx->ctx_doi = XFRM_SC_DOI_LSM;
        ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
-       ctx->ctx_len = str_len;
+       ctx->ctx_len = str_len + 1;
        memcpy(ctx->ctx_str, &uctx[1], str_len);
        ctx->ctx_str[str_len] = '\0';
        rc = security_context_to_sid(&selinux_state, ctx->ctx_str, str_len,