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, 106 insertions, 0 deletions

diff --git a/include/net/smc.h b/include/net/smc.h
new file mode 100644
index 000000000..a2bc3ab88
--- /dev/null
+++ b/include/net/smc.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Shared Memory Communications over RDMA (SMC-R) and RoCE
+ *
+ *  Definitions for the SMC module (socket related)
+ *
+ *  Copyright IBM Corp. 2016
+ *
+ *  Author(s):  Ursula Braun <ubraun@linux.vnet.ibm.com>
+ */
+#ifndef _SMC_H
+#define _SMC_H
+
+#include <linux/device.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+#include <linux/dibs.h>
+
+struct tcp_sock;
+struct inet_request_sock;
+struct sock;
+
+#define SMC_MAX_PNETID_LEN	16	/* Max. length of PNET id */
+
+struct smc_hashinfo {
+	rwlock_t lock;
+	struct hlist_head ht;
+};
+
+/* SMCD/ISM device driver interface */
+#define ISM_RESERVED_VLANID	0x1FFF
+
+struct smcd_gid {
+	u64	gid;
+	u64	gid_ext;
+};
+
+struct smcd_dev {
+	struct dibs_dev *dibs;
+	struct list_head list;
+	spinlock_t lock;
+	struct list_head vlan;
+	struct workqueue_struct *event_wq;
+	u8 pnetid[SMC_MAX_PNETID_LEN];
+	bool pnetid_by_user;
+	struct list_head lgr_list;
+	spinlock_t lgr_lock;
+	atomic_t lgr_cnt;
+	wait_queue_head_t lgrs_deleted;
+	u8 going_away : 1;
+	struct smc_connection *conn[];
+};
+
+#define SMC_HS_CTRL_NAME_MAX 16
+
+enum {
+	/* ops can be inherit from init_net */
+	SMC_HS_CTRL_FLAG_INHERITABLE = 0x1,
+
+	SMC_HS_CTRL_ALL_FLAGS = SMC_HS_CTRL_FLAG_INHERITABLE,
+};
+
+struct smc_hs_ctrl {
+	/* private */
+
+	struct list_head list;
+	struct module *owner;
+
+	/* public */
+
+	/* unique name */
+	char name[SMC_HS_CTRL_NAME_MAX];
+	int flags;
+
+	/* Invoked before computing SMC option for SYN packets.
+	 * We can control whether to set SMC options by returning various value.
+	 * Return 0 to disable SMC, or return any other value to enable it.
+	 */
+	int (*syn_option)(struct tcp_sock *tp);
+
+	/* Invoked before Set up SMC options for SYN-ACK packets
+	 * We can control whether to respond SMC options by returning various
+	 * value. Return 0 to disable SMC, or return any other value to enable
+	 * it.
+	 */
+	int (*synack_option)(const struct tcp_sock *tp,
+			     struct inet_request_sock *ireq);
+};
+
+#if IS_ENABLED(CONFIG_SMC_HS_CTRL_BPF)
+#define smc_call_hsbpf(init_val, tp, func, ...) ({				\
+	typeof(init_val) __ret = (init_val);					\
+	struct smc_hs_ctrl *ctrl;						\
+	rcu_read_lock();							\
+	ctrl = rcu_dereference(sock_net((struct sock *)(tp))->smc.hs_ctrl);	\
+	if (ctrl && ctrl->func)							\
+		__ret = ctrl->func(tp, ##__VA_ARGS__);				\
+	rcu_read_unlock();							\
+	__ret;									\
+})
+#else
+#define smc_call_hsbpf(init_val, tp, ...)  ({ (void)(tp); (init_val); })
+#endif /* CONFIG_SMC_HS_CTRL_BPF */
+
+#endif	/* _SMC_H */