SUNRPC: auth_gss: fix memory leaks in XDR decoding error paths

From: Chuck Lever <[email protected]>

The gssx_dec_ctx(), gssx_dec_status(), and gssx_dec_name() functions allocate memory via gssx_dec_buffer(), which calls kmemdup(). When a subsequent decode operation fails, these functions return immediately without freeing previously allocated buffers, causing memory leaks.

The leak in gssx_dec_ctx() is particularly relevant because the caller (gssp_accept_sec_context_upcall) initializes several buffer length fields to non-zero values, resulting in memory allocation:

struct gssx_ctx rctxh = {
.exported_context_token.len = GSSX_max_output_handle_sz, .mech.len = GSS_OID_MAX_LEN, .src_name.display_name.len = GSSX_max_princ_sz, .targ_name.display_name.len = GSSX_max_princ_sz
};

If, for example, gssx_dec_name() succeeds for src_name but fails for targ_name, the memory allocated for exported_context_token, mech, and src_name.display_name remains unreferenced and cannot be reclaimed.

Add error handling with goto-based cleanup to free any previously allocated buffers before returning an error.

Reported-by Xingjing Deng <[email protected]>

Closes https://lore.kernel.org/linux-nfs/CAK+ZN9qttsFDu6h1FoqGadXjMx1QXqPMoYQ=6O9RY4SxVTvKng@mail.gmail.com/ open here

Fixes 1d658336b05f ("SUNRPC: Add RPC based upcall mechanism for RPCGSS auth")

Cc [email protected]

Signed-off-by Chuck Lever <[email protected]>

---
 net/sunrpc/auth_gss/gss_rpc_xdr.c | 82 ++++++++++++++++++++++++-------
 1 file changed, 64 insertions(+), 18 deletions(-)

net/sunrpc/auth_gss/gss_rpc_xdr.c +57 -18

index 7d2cdc2bd374..f320c0a8e604 100644
@@ -320,29 +320,47 @@ static int gssx_dec_status(struct xdr_stream *xdr,
 
 	/* status->minor_status */
 	p = xdr_inline_decode(xdr, 8);
-	if (unlikely(p == NULL))
-		return -ENOSPC;
+	if (unlikely(p == NULL)) {
+		err = -ENOSPC;
+		goto out_free_mech;
+	}
 	p = xdr_decode_hyper(p, &status->minor_status);
 
 	/* status->major_status_string */
 	err = gssx_dec_buffer(xdr, &status->major_status_string);
 	if (err)
-		return err;
+		goto out_free_mech;
 
 	/* status->minor_status_string */
 	err = gssx_dec_buffer(xdr, &status->minor_status_string);
 	if (err)
-		return err;
+		goto out_free_major_status_string;
 
 	/* status->server_ctx */
 	err = gssx_dec_buffer(xdr, &status->server_ctx);
 	if (err)
-		return err;
+		goto out_free_minor_status_string;
 
 	/* we assume we have no options for now, so simply consume them */
 	/* status->options */
 	err = dummy_dec_opt_array(xdr, &status->options);
+	if (err)
+		goto out_free_server_ctx;
 
+	return 0;
+
+out_free_server_ctx:
+	kfree(status->server_ctx.data);
+	status->server_ctx.data = NULL;
+out_free_minor_status_string:
+	kfree(status->minor_status_string.data);
+	status->minor_status_string.data = NULL;
+out_free_major_status_string:
+	kfree(status->major_status_string.data);
+	status->major_status_string.data = NULL;
+out_free_mech:
+	kfree(status->mech.data);
+	status->mech.data = NULL;
 	return err;
 }
 

@@ -505,28 +523,35 @@ static int gssx_dec_name(struct xdr_stream *xdr,
 	/* name->name_type */
 	err = gssx_dec_buffer(xdr, &dummy_netobj);
 	if (err)
-		return err;
+		goto out_free_display_name;
 
 	/* name->exported_name */
 	err = gssx_dec_buffer(xdr, &dummy_netobj);
 	if (err)
-		return err;
+		goto out_free_display_name;
 
 	/* name->exported_composite_name */
 	err = gssx_dec_buffer(xdr, &dummy_netobj);
 	if (err)
-		return err;
+		goto out_free_display_name;
 
 	/* we assume we have no attributes for now, so simply consume them */
 	/* name->name_attributes */
 	err = dummy_dec_nameattr_array(xdr, &dummy_name_attr_array);
 	if (err)
-		return err;
+		goto out_free_display_name;
 
 	/* we assume we have no options for now, so simply consume them */
 	/* name->extensions */
 	err = dummy_dec_opt_array(xdr, &dummy_option_array);
+	if (err)
+		goto out_free_display_name;
 
+	return 0;
+
+out_free_display_name:
+	kfree(name->display_name.data);
+	name->display_name.data = NULL;
 	return err;
 }
 

@@ -649,32 +674,34 @@ static int gssx_dec_ctx(struct xdr_stream *xdr,
 	/* ctx->state */
 	err = gssx_dec_buffer(xdr, &ctx->state);
 	if (err)
-		return err;
+		goto out_free_exported_context_token;
 
 	/* ctx->need_release */
 	err = gssx_dec_bool(xdr, &ctx->need_release);
 	if (err)
-		return err;
+		goto out_free_state;
 
 	/* ctx->mech */
 	err = gssx_dec_buffer(xdr, &ctx->mech);
 	if (err)
-		return err;
+		goto out_free_state;
 
 	/* ctx->src_name */
 	err = gssx_dec_name(xdr, &ctx->src_name);
 	if (err)
-		return err;
+		goto out_free_mech;
 
 	/* ctx->targ_name */
 	err = gssx_dec_name(xdr, &ctx->targ_name);
 	if (err)
-		return err;
+		goto out_free_src_name;
 
 	/* ctx->lifetime */
 	p = xdr_inline_decode(xdr, 8+8);
-	if (unlikely(p == NULL))
-		return -ENOSPC;
+	if (unlikely(p == NULL)) {
+		err = -ENOSPC;
+		goto out_free_targ_name;
+	}
 	p = xdr_decode_hyper(p, &ctx->lifetime);
 
 	/* ctx->ctx_flags */

@@ -683,17 +710,36 @@ static int gssx_dec_ctx(struct xdr_stream *xdr,
 	/* ctx->locally_initiated */
 	err = gssx_dec_bool(xdr, &ctx->locally_initiated);
 	if (err)
-		return err;
+		goto out_free_targ_name;
 
 	/* ctx->open */
 	err = gssx_dec_bool(xdr, &ctx->open);
 	if (err)
-		return err;
+		goto out_free_targ_name;
 
 	/* we assume we have no options for now, so simply consume them */
 	/* ctx->options */
 	err = dummy_dec_opt_array(xdr, &ctx->options);
+	if (err)
+		goto out_free_targ_name;
 
+	return 0;
+
+out_free_targ_name:
+	kfree(ctx->targ_name.display_name.data);
+	ctx->targ_name.display_name.data = NULL;
+out_free_src_name:
+	kfree(ctx->src_name.display_name.data);
+	ctx->src_name.display_name.data = NULL;
+out_free_mech:
+	kfree(ctx->mech.data);