ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faultsgrafted

When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set,
a user fault may trigger show_pte() without any lock.
If another thread in the same process concurrently calls munmap(),
the page table pages may be freed while show_pte() is still traversing
them, causing a use-after-free in show_pte().

If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table
of PMD are freed when show_pte() is running.

Acquire mmap_write_lock() around show_pte() for user faults to fix the
contention.

For user faults, additionally restrict that show_pte() is called only
when the addr is a user-space address (addr < TASK_SIZE). This is because
the lock of tsk->mm only protects the virtual memory of user address space,
furthermore, dumping the page tables of a kernel-space address for user
faults is unnecessary and may have security implications.

Keep everything unchanged for kernel faults, because the kernel is
already in the "oops" state, acquiring a lock may risk a deadlock.

Co-developed-by: Qi Xi <xiqi2@huawei.com>

Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults")
Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 115 insertions, 0 deletions

diff --git a/include/net/af_rxrpc.h b/include/net/af_rxrpc.h
new file mode 100644
index 000000000..0fb4c41c9
--- /dev/null
+++ b/include/net/af_rxrpc.h
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* RxRPC kernel service interface definitions
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _NET_RXRPC_H
+#define _NET_RXRPC_H
+
+#include <linux/rxrpc.h>
+#include <linux/ktime.h>
+
+struct key;
+struct sock;
+struct socket;
+struct rxrpc_call;
+struct rxrpc_peer;
+struct krb5_buffer;
+enum rxrpc_abort_reason;
+
+enum rxrpc_interruptibility {
+	RXRPC_INTERRUPTIBLE,	/* Call is interruptible */
+	RXRPC_PREINTERRUPTIBLE,	/* Call can be cancelled whilst waiting for a slot */
+	RXRPC_UNINTERRUPTIBLE,	/* Call should not be interruptible at all */
+};
+
+enum rxrpc_oob_type {
+	RXRPC_OOB_CHALLENGE,	/* Security challenge for a connection */
+};
+
+/*
+ * Debug ID counter for tracing.
+ */
+extern atomic_t rxrpc_debug_id;
+
+/*
+ * Operations table for rxrpc to call out to a kernel application (e.g. kAFS).
+ */
+struct rxrpc_kernel_ops {
+	void (*notify_new_call)(struct sock *sk, struct rxrpc_call *call,
+				unsigned long user_call_ID);
+	void (*discard_new_call)(struct rxrpc_call *call, unsigned long user_call_ID);
+	void (*user_attach_call)(struct rxrpc_call *call, unsigned long user_call_ID);
+	void (*notify_oob)(struct sock *sk, struct sk_buff *oob);
+};
+
+typedef void (*rxrpc_notify_rx_t)(struct sock *, struct rxrpc_call *,
+				  unsigned long);
+typedef void (*rxrpc_notify_end_tx_t)(struct sock *, struct rxrpc_call *,
+				      unsigned long);
+
+void rxrpc_kernel_set_notifications(struct socket *sock,
+				    const struct rxrpc_kernel_ops *app_ops);
+struct rxrpc_call *rxrpc_kernel_begin_call(struct socket *sock,
+					   struct rxrpc_peer *peer,
+					   struct key *key,
+					   unsigned long user_call_ID,
+					   s64 tx_total_len,
+					   u32 hard_timeout,
+					   gfp_t gfp,
+					   rxrpc_notify_rx_t notify_rx,
+					   u16 service_id,
+					   bool upgrade,
+					   enum rxrpc_interruptibility interruptibility,
+					   unsigned int debug_id);
+int rxrpc_kernel_send_data(struct socket *, struct rxrpc_call *,
+			   struct msghdr *, size_t,
+			   rxrpc_notify_end_tx_t);
+int rxrpc_kernel_recv_data(struct socket *, struct rxrpc_call *,
+			   struct iov_iter *, size_t *, bool, u32 *, u16 *);
+bool rxrpc_kernel_abort_call(struct socket *, struct rxrpc_call *,
+			     u32, int, enum rxrpc_abort_reason);
+void rxrpc_kernel_shutdown_call(struct socket *sock, struct rxrpc_call *call);
+void rxrpc_kernel_put_call(struct socket *sock, struct rxrpc_call *call);
+struct rxrpc_peer *rxrpc_kernel_lookup_peer(struct socket *sock,
+					    struct sockaddr_rxrpc *srx, gfp_t gfp);
+void rxrpc_kernel_put_peer(struct rxrpc_peer *peer);
+struct rxrpc_peer *rxrpc_kernel_get_peer(struct rxrpc_peer *peer);
+struct rxrpc_peer *rxrpc_kernel_get_call_peer(struct socket *sock, struct rxrpc_call *call);
+const struct sockaddr_rxrpc *rxrpc_kernel_remote_srx(const struct rxrpc_peer *peer);
+const struct sockaddr *rxrpc_kernel_remote_addr(const struct rxrpc_peer *peer);
+unsigned long rxrpc_kernel_set_peer_data(struct rxrpc_peer *peer, unsigned long app_data);
+unsigned long rxrpc_kernel_get_peer_data(const struct rxrpc_peer *peer);
+unsigned int rxrpc_kernel_get_srtt(const struct rxrpc_peer *);
+int rxrpc_kernel_charge_accept(struct socket *sock, rxrpc_notify_rx_t notify_rx,
+			       unsigned long user_call_ID, gfp_t gfp,
+			       unsigned int debug_id);
+void rxrpc_kernel_set_tx_length(struct socket *, struct rxrpc_call *, s64);
+bool rxrpc_kernel_check_life(const struct socket *, const struct rxrpc_call *);
+
+int rxrpc_sock_set_min_security_level(struct sock *sk, unsigned int val);
+int rxrpc_sock_set_security_keyring(struct sock *, struct key *);
+int rxrpc_sock_set_manage_response(struct sock *sk, bool set);
+
+enum rxrpc_oob_type rxrpc_kernel_query_oob(struct sk_buff *oob,
+					   struct rxrpc_peer **_peer,
+					   unsigned long *_peer_appdata);
+struct sk_buff *rxrpc_kernel_dequeue_oob(struct socket *sock,
+					 enum rxrpc_oob_type *_type);
+void rxrpc_kernel_free_oob(struct sk_buff *oob);
+void rxrpc_kernel_query_challenge(struct sk_buff *challenge,
+				  struct rxrpc_peer **_peer,
+				  unsigned long *_peer_appdata,
+				  u16 *_service_id, u8 *_security_index);
+int rxrpc_kernel_reject_challenge(struct sk_buff *challenge, u32 abort_code,
+				  int error, enum rxrpc_abort_reason why);
+int rxkad_kernel_respond_to_challenge(struct sk_buff *challenge);
+u32 rxgk_kernel_query_challenge(struct sk_buff *challenge);
+int rxgk_kernel_respond_to_challenge(struct sk_buff *challenge,
+				     struct krb5_buffer *appdata);
+u8 rxrpc_kernel_query_call_security(struct rxrpc_call *call,
+				    u16 *_service_id, u32 *_enctype);
+
+#endif /* _NET_RXRPC_H */