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 --- fs/btrfs/dev-replace.h | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 fs/btrfs/dev-replace.h (limited to 'fs/btrfs/dev-replace.h') diff --git a/fs/btrfs/dev-replace.h b/fs/btrfs/dev-replace.h new file mode 100644 index 000000000..b35cecf38 --- /dev/null +++ b/fs/btrfs/dev-replace.h @@ -0,0 +1,41 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) STRATO AG 2012. All rights reserved. + */ + +#ifndef BTRFS_DEV_REPLACE_H +#define BTRFS_DEV_REPLACE_H + +#include +#include + +struct btrfs_ioctl_dev_replace_args; +struct btrfs_fs_info; +struct btrfs_trans_handle; +struct btrfs_dev_replace; +struct btrfs_block_group; +struct btrfs_device; + +int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info); +int btrfs_run_dev_replace(struct btrfs_trans_handle *trans); +int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info, + struct btrfs_ioctl_dev_replace_args *args); +void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info, + struct btrfs_ioctl_dev_replace_args *args); +int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info); +void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info); +int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info); +bool __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace); +bool btrfs_finish_block_group_to_copy(struct btrfs_device *srcdev, + struct btrfs_block_group *cache, + u64 physical); +void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info); +void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount); + +static inline void btrfs_bio_counter_dec(struct btrfs_fs_info *fs_info) +{ + btrfs_bio_counter_sub(fs_info, 1); +} + + +#endif -- cgit v1.3.1