From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults 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 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) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- include/net/failover.h | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 include/net/failover.h (limited to 'include/net/failover.h') diff --git a/include/net/failover.h b/include/net/failover.h new file mode 100644 index 000000000..f2b42b4b9 --- /dev/null +++ b/include/net/failover.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (c) 2018, Intel Corporation. */ + +#ifndef _FAILOVER_H +#define _FAILOVER_H + +#include + +struct failover_ops { + int (*slave_pre_register)(struct net_device *slave_dev, + struct net_device *failover_dev); + int (*slave_register)(struct net_device *slave_dev, + struct net_device *failover_dev); + int (*slave_pre_unregister)(struct net_device *slave_dev, + struct net_device *failover_dev); + int (*slave_unregister)(struct net_device *slave_dev, + struct net_device *failover_dev); + int (*slave_link_change)(struct net_device *slave_dev, + struct net_device *failover_dev); + int (*slave_name_change)(struct net_device *slave_dev, + struct net_device *failover_dev); + rx_handler_result_t (*slave_handle_frame)(struct sk_buff **pskb); +}; + +struct failover { + struct list_head list; + struct net_device __rcu *failover_dev; + netdevice_tracker dev_tracker; + struct failover_ops __rcu *ops; +}; + +struct failover *failover_register(struct net_device *dev, + struct failover_ops *ops); +void failover_unregister(struct failover *failover); +int failover_slave_unregister(struct net_device *slave_dev); + +#endif /* _FAILOVER_H */ -- cgit v1.3.1